Wednesday, December 31, 2008

Bulk Flow Functions in long-distance Transport

This type of transport is usually along the vertical axis of the plant from root to leaves and vice versa. Vascular tissues are involved in this type of transport, as diffusion would be too slow. Bulk flow (movement due to pressure differences) moves water and solutes through xylem vessels and sieve tubes. Transpiration reduces pressure in the leaf xylem; this creates a tension, which pulls sap up through the xylem from the roots. Hydrostatic pressure develops at one end of the sieve tubes in the phloem; this forces the sap to the other end of the tube.

Absorption of water and minerals by roots: Water and minerals enter through the root epidermis, cross the cortex, pass into the stele, and are carried upward in the xylem.

Active accumulation of mineral ions: The cells cannot get enough mineral ions from the soil by diffusion alone. The soils solution is too dilute. Active transport of these ions must occur. Specific carrier proteins 'in the plasma membrane attract and carry their specific mineral into the cell. H+ is pumped out of the cell causing a change in pH and a voltage across the membrane. This helps drive the anions and cations into the cell. Water and minerals cross the cortex either by symplast, which is the living continuum of cytoplasm, connected by plasmodesmata or by apoplast, which is nonliving matrix of cell walls. At the endodermis the casparian strip blocks the apoplastic route. This is a ring of suberin around each endodermal cell. Here, water and minerals must enter the stele through the cells of the endodermis. Water and minerals enter the stele via symplast, but xylem is part of the apoplast. Transfer cells selectively pump ions out of the symplast into the apoplast so they may enter the xylem. This action requires energy.

The ascent of xylem sap depends mainly on transpiration and the physical properties of water. The shoot depends on the efficient delivery of its water supply. Xylem carries sap containing dissolved mineral and nutrients from the roots to the leaves. Water is pulled up through the xylem by the force of transpiration. Water transported up from roots must replace that lost through transpiration. The connection between the xylem gives a continuous column of water to form between roots and leaves. This column acts like a thread that moves upward by the pull of transpiration. Transpiration pulls the xylem sap upward, and cohesion of water transmits the upward pull along the entire length of xylem. The forces responsible for the ascent of sap through xylem are Transpiration, Adhesion, Cohesion, and Tension (TACT).

Monday, December 29, 2008

Active and Passive Transport of Solutes


The plasma membrane's selective permeability controls the movement of solutes between a plant cell and the extracellular fluids. Solutes may move by passive or active transport. 

Passive transport occurs when a solute molecule diffuses across a membrane down a concentration gradient with no direct expenditure of energy by the cell. Transport proteins embedded in the cell membrane may increase the speed at which solutes cross. Transport proteins may facilitate diffusion by serving as carrier proteins or forming selective channels. Carrier proteins bind selectively to a solute molecule on one side of the membrane, undergo a conformational change, and release the solute molecule on the opposite side of the membrane. Selective channels are passageways by which selective molecules may enter and leave a cell; some gated selective channels are stimulated to open or close by environmental conditions.

Active transport occurs when a solute molecule is moved across a membrane against a concentration gradient. It is an energy-requiring process. The proton pump is an active transporter important to plants. 

Water Potential and Osmosis

Osmosis results in the net uptake or loss of water by the cell and depends on which component, the cell or extracellular fluids, has the highest water potential. Water potential is the free energy of water that is a consequence of solute concentration and applied pressure. Water potential is the physical property predicting the direction of water flow. Water will always move across the membrane from the solution with the higher water potential to the one with lower water potential. Pure water has a water potential of zero, and addition of solutes lowers water potential into the negative range. Increased pressure raises the water potential into the positive range. A negative pressure may also move water across a membrane; this bulk flow (movement of water due to pressure differences) is usually faster than movement caused by different solute concentrations. Plant cells will gain or lose water to intercellular fluids depending upon their water potential. 

A flaccid cell placed in a hyperosmotic solution will lose water by osmosis; the cell will plasmolyze (protoplast moves away from cell wall). A flaccid cell placed in a hypoosmotic solution will gain water by osmosis; the cell will swell and a turgor pressure develops; when pressure from the cell wall is equal to the osmotic pressure, equilibrium is reached and no net movement of water occurs. 

Transport Within Tissues and Organs

The symplast and apoplast both function in transport within tissues and organs. Lateral transport is usually along the radial axis of plant organs, and can occur by three routes in plant tissues and organs. These are:

1. Across the plasma membrane and cell walls. Solutes move from one cell to the next by repeatedly crossing plasma membranes and cell walls. 
2. The symplast route. A symplast is the continuum of cytoplasm within a plant tissue formed by the plasmodesmata, which passes through pores in the cell walls. Once water or a solute enters a cell by crossing a plasma membrane, the molecules can enter other cells by traveling through plasmodesmata. 
3. The apoplast route. An apoplast is the continuum between plant cells, which is formed between the continuous matrix of cell walls. Water and solute molecules can move from one area of a root or other organ via the apoplast without entering a cell.

Water and solute molecules can move laterally in a plant organ by anyone of these routes or by switching from one to another. 

Sunday, December 28, 2008

Internal Transport in Plants

Land plants require a transport system because unlike their aquatic ancestors, photosynthetic plant organs have no direct access to water and minerals. The internal transport of plant system involves the lifting of water and minerals to great heights to the tips of all branches and leaves, against the gravitational pull.

Three levels of transport occur in plants:

1. Uptake of water and solutes by individual cells.
2. Short-distance, cell-to-cell transport at the level of tissues and organs.
3. Long-distance transport of sap in xylem and phloem at the whole-plant level.

Transport at the cellular level depends on the selective permeabilities of membranes.

Active and Passive Transport of Solutes

The plasma membrane's selective permeability controls the movement of solutes between a plant cell and the extracellular fluids. Solutes may move by passive or active transport.

Passive transport occurs when a solute molecule diffuses across a membrane down a concentration gradient with no direct expenditure of energy by the cell. Transport proteins embedded in the cell membrane may increase the speed at which solutes cross. Transport proteins may facilitate diffusion by serving as carrier proteins or forming selective channels. Carrier proteins bind selectively to a solute molecule on one side of the membrane, undergo a conformational change, and release the solute molecule on the opposite side of the membrane. Selective channels are passageways by which selective molecules may enter and leave a cell; some gated selective channels are stimulated to open or close by environmental conditions.

Active transport occurs when a solute molecule is moved across a membrane against a concentration gradient. It is an energy-requiring process. The proton pump is an active transporter important to plants.

Internal Transport in Animals

All animals must maintain a homeostatic balance in their bodies. This requires the circulation of nutrients, metabolic wastes, and respiratory gases through the animal's body. Multicellular animals do not have most of their cells in contact with the external environment and so have developed circulatory systems to transport nutrients, oxygen, carbon dioxide, and metabolic wastes. Components of the circulatory system include:

Blood: a connective tissue of liquid plasma and cells.
Heart: a muscular pump to move the blood.
Blood vessels: arteries, capillaries and veins that deliver blood to all tissues.

There are several types of circulatory systems. Organisms, such as hydra, have a fluid-filled, internal gastrovascular cavity. This cavity supplies nutrients for all body cells lining the cavity, obtains oxygen from the water in the cavity, and releases carbon dioxide and other wastes into it. The gastrovascular cavity of a flatworm, such as the planarian, is more complex than that of the hydra. The open circulatory system is common to molluscs and arthropods. Open circulatory systems (evolved in insects, mollusks, and other invertebrates) pump blood into a hemocoel with the blood diffusing back to the circulatory system between cells. Blood is pumped by a heart into the body cavities, where tissues are surrounded by the blood. The resulting blood flow is sluggish.

Higher animals such as vertebrates, and a few invertebrates, have a closed circulatory system. Closed circulatory systems have the blood enclosed within blood.

Higher animals such as vertebrates, and a few invertebrates, have a closed circulatory system. Closed circulatory systems have the blood enclosed within blood vessels of different sizes and wall thicknesses. It is not released in between the cells. In this type of system, blood is pumped by a heart through vessels, and does not normally fill body cavities. Blood flow is not sluggish. Hemoglobin causes vertebrate blood to turn red in the presence of oxygen; but more importantly, hemoglobin molecules in blood cells transport oxygen. The closed circulatory system present in humans is called the cardiovascular system. A circulatory or cardiovascular system is a specialized system that moves the fluid medium, hemolymph or blood, in a specific direction determined by the presence of unidirectional blood vessels.

The vertebrate cardiovascular system includes a heart, which is a muscular pump that contracts to propel blood out to the body through arteries, and a series of blood vessels. The upper chamber of the heart, the atrium, is where the blood enters the heart. Passing through a valve, blood enters the lower chamber, the ventricle. Contraction of the ventricle forces blood from the heart through an artery. The heart muscle is composed of cardiac muscle cells. Arteries are blood vessels that carry blood away from heart. Arterial walls are able to expand and contract. The aorta is the main artery leaving the heart. The pulmonary artery carries deoxygenated blood to the lungs. In the lungs, gas exchange occurs-earbon dioxide diffuses out and oxygen diffuses in. Arterioles are small arteries that branch into collections of capillaries known as capillary beds. Capillaries are thin-walled blood vessels in which gas exchange occurs. Capillaries are concentrated into capillary beds. Nutrients, wastes, and hormones are exchanged across the thin walls of capillaries.

The circulatory system functions in the delivery of oxygen, nutrient molecules, and hormones and the removal of carbon dioxide, ammonia, and other metabolic wastes. Capillaries are the points of exchange between the blood and surrounding tissues. Materials cross in and out of the capillaries by passing through or between the cells that line the capillary. Blood leaving the capillary beds is collected into a progressively larger series of venules (venules are smaller veins that gather blood from capillary beds into veins), which in turn join to form veins. Veins carry blood from capillaries to the heart. With the exception of the pulmonary veins, blood in veins is oxygen-poor. The pulmonary veins carry oxygenated blood from lungs back to the heart.

Saturday, December 27, 2008

Internal Transport


Living things must be capable of transporting nutrients, wastes, and gases to and from cells. Single-celled organisms use their cell surface as a point of exchange with the outside environment. Multicellular organisms have developed transport and circulatory systems to deliver oxygen and food to cells and remove carbon dioxide and metabolic wastes. Simple multicellular organisms such as sponges, multicellular fungi, and algae have a transport system. Sea water is the medium of transport and is propelled in and out of the sponge by ciliary action. Simple animals, such as hydra and planaria, lack specialized organs such as hearts and blood vessels, and instead use their skin as an exchange point for materials. This, however, limits the size an animal can attain. To become larger, they need specialized organs and organ systems. In lower plants such as algae and fungi, transport of material takes place through the body surface and cytoplasmic streaming movements.

Any system of moving fluids which reduces the functional diffusion distance that nutrients, wastes, and gases must traverse may be referred to as an internal transport or circulatory system.

Gasesous Exchange in Cell Division

All living organisms exchange carbon dioxide and oxygen with their environment for carrying out different functions. Organisms must exchange gases with their environment in order to carry out photosynthesis, cellular respiration, and other essential processes. This gas exchange is accomplished exclusively through passive diffusion.

Oxygen and carbon dioxide are the two most important gases that organisms exchange. Certain microorganisms are also capable of taking up nitrogen gas for the purpose of nitrogen fixation. Three primary factors govern gas exchange: the concentration gradient of the gas, the amount of surface area available for gas exchange, and the distance over which the diffusion takes place. Gas concentrations differ between air and water. The concentration of oxygen is much higher in air than in water, whereas carbon dioxide concentration is similar in both. Density differences between water and air influence the uptake of gases. Diffusion is slower in water because water is denser than air. Aquatic organisms must therefore move large quantities of water over their gas exchange surfaces to get the same amount of gas found in a much smaller volume of air. Oxygen has a higher concentration in the atmosphere than does carbon dioxide. Oxygen therefore diffuses into animals more rapidly than carbon dioxide diffuses into plants.

Organisms use different methods and organs for the purpose of gas exchange, which depends on their habitat.

Body surface

Small organisms and plants accomplish gas exchange by simple diffusion across their cell or body surfaces. Multicellular organisms, which have a large surface area relative to their body volume, exchange gases across their body surface. Earthworms, algae, etc. are examples. Body surfaces specialized for gas exchange are moist, which allows easy exchange of gases.


Larger, more complex organisms use specialized gas exchange structures such as gills and lungs. Gills provide large surface area for gas exchange. Gills are convoluted growths covered by thin epithelial layers, containing.a rich supply of blood vessels. Since gases cannot reach individual hody cells directly from these structures, large organisms use transport fluids to move gases around their bodies. The surface area devoted to gas exchange in an organism is directly proportional to the organism's size and metabolic needs. Gas exchange on land is a problem because of the water loss associated with exposing the exchange surfaces to dry air. Terrestrial gas' exchange is thus a compromise between obtaining necessary gases and avoiding water loss.

Tracheal system

This is a network of tubes present in insects. These tracheal systems open outside through openings called spiracles, through which oxygen enters into the network of tubes. Thus, there is direct exchange of gases between the cells and the tracheal tubes.


These are the structures present in the lungs. Lungs are the well-developed organ system for the effective exchange of gases between atmosphere and the blood present in the terrestrial organisms. Lungs are elastic sacs that allow the animal to pump air in and out of the body. The trachea of the lungs divide into two branches, which in turn divide into many sub-branches known as bronchioles. The bronchioles end in small, thin-walled sacs known as alveoli. The presence of alveoli increases the effective surface area for gaseous exchange. Alveoli have a rich supply of fine blood vessels with very thin walls through which gas can easily diffuse into and out.

Gas Exchange In Plants

In plants gas exchange usually takes place through stomata, small openings present on the epidermis of the leaves. The stomata open into spongy parenchyma and the gas exchange takes place between the cells and the gas filled in the air space. Gas exchange is needed for both respiration and photosynthesis. 

Friday, December 26, 2008


The energy that powers life comes from the sun. Producers are organisms that capture sunlight energy through photosynthesis and store it in organic molecules. They obtain all the energy and inorganic materials they need directly from the environment. Consumers are organisms that harvest energy and chemicals from premade organic molecules contained in the bodies of other organisms. Nutrition is the method by which organisms obtain materials and energy needed for sustaining life. Animals, plants, and microbes have different methods to obtain energy from sources and nutrients from the environment.

Elements of Nutrition

Organisms depend on only a small number of elements to sustain life. These include carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. Of these, carbon, hydrogen, and oxygen form the framework of organic molecules such as carbohydrates, proteins, fats, and nucleic acids. The other elements are restricted in distribution. Sulfur and nitrogen are present in proteins; phosphorous and nitrogen are present in nucleic acids. Many other elements also have equally important and essential roles similar to that of the biomolecules such as proteins carbohydrates, lipids, and nucleic acids. They may not be present as a component of macromolecules, but may be present as ions or as a part of other organic molecules such as vitamins and cofactors. There are a group of elements known as microelements or trace elements, which are required only in very small quantities but play an important role in metabolism. So as nutrients they are very important. Elements such as manganese, copper, zinc, cobalt selenium, and iodine are important microelements.

Plant Nutrition

Autotropic organisms such as plants are the producers of the ecosystem. Producers are organisms that capture sunlight energy through photosynthesis and store it in organic molecules. They obtain all the energy and inorganic materials they need directly from the environment. Consumers are organisms that harvest energy and chemicals from premade organic molecules contained in the bodies of other organisms. Green plants absorb light energy and inorganic molecules such as water and carbon dioxide from the environment and synthesize glucose molecules with a process known as photosynthesis. These molecules can be further modified into other types of biomolecules such as amino acids, lipids, vitamins, etc.

The chlorophyll-containing parts of the plants such as leaves are the sites of photosynthesis. The leaves are the organs specially designed to trap the maximum amount of sunlight energy and transform it into a usable form of chemical energy in organic molecules such as lipids, carbohydrates, and proteins. Leaves are flat exposing a maximum surface area against sunlight with its photosynthetic tissue, the palisade parenchyma on the upper surface. The spongy parenchyma specialized in the absorption of carbon dioxide are present on the lower half of the leaf tissue.

The root hairs are the organs adapted for the absorption of water and minerals from the soil. The root hairs are the thin-walled extension of the epidermal cells of the root and have a big vacuole in the middle. Root hairs provide increased surface area for the absorption of water and minerals actively (using energy) or passively (by osmosis). Higher plants are also able to convert inorganic nitrogen (nitrates, nitrites, and ammonia) into organic nitrogens such as amino acids and proteins but they cannot utilize elemental forms of nitrogen even though it is abundant in the atmosphere. They are also able to synthesize all types of fatty acids and other vitamins needed. But plants have symbiotic association with nitrogen-fixing bacteria. These bacteria living in the root nodules can absorb elemental forms of nitrogen and can be converted to nitrates and ammonia, and that will be further transformed into organic forms by host plants. Plants of the legume family have the symbiotic association of nitrogen-fixing bacteria in their root nodules.

Animal Nutrition

Animals and all other organisms that depend on organic food materials synthesized by producers are called heterotrophs and form the consumers of the ecosystem. The biomolecules synthesized by the green plants are the sources of energy and raw materials for the synthesis of new biomolecules needed by their systems. For example, animals consume the protein of plants and in the stomach it is converted into amino acids. These amino acids are absorbed into the cells and are used as the starting materials for the synthesis of new protein molecules. But animals are unable to synthesize amino acids. Organisms must first digest the complex macromolecules in their food before absorbing simpler chemicals into their bodies. In animals, food is first mechanically broken down and then chemically digested before being absorbed. The amount of absorptive surface area that organisms devote to nutrient acquisition is related to the type of nutrients they need. Most organisms use active transport to absorb nutrients, and large absorptive surface areas increase the rate of transport.

Some bacteria in the digestive track help the animals with their nutrition by providing some essential vitamins. Vitamins are nutrients needed in the diet in very small quantities but are very essential for normal functions of the system. Animals cannot synthesize most vitamins and should be supplemented along with the diet. There are two types of vitamins-fat-soluble vitamins (A, D, and E) and water-soluble vitamins (all B complex vitamins, C, and folic acid). Defidencyof any of the nutrients, micronutrients, or macronutrients can cause serious diseases or disorders or even deformities in the system. For example, lack of proteins in the diet can cause stunted growth in children and deficiency of certain vitamins and iron can cause anemia. Deficiency of vitamin B complex can lead to the problems related to the nervous system. The absence of vitamin C can cause scurvy (bleeding gums), deficiency of vitamin A can cause weak eyesight, and deficiency of vitamin D causes bone deformities.

The heterotrophs are classified according to the mode of nutrition. Those organisms which directly depend on the producers, are the herbivores and those animals that eat other animals are the carnivores. There are some organisms that depend on the dead organic matter of both plants animals and they are the saprophytes or (detritivores). The digestive systems of animals are diverse, but show common structural features. Most have one-way flow that allows specialized activities such as chewing, storage, digestion, absorption, and the elimination of wastes. Unlike plants, animals can move and forage for their food. Herbivores and highly mobile predators use active foraging, while less mobile predators employ sit-and-wait foraging, often with the aid of a trapping mechanism. In animals, the more difficult the diet is to digest, the more digestive specializations are present to increase the rate of nutrient acquisition. Large herbivores, in particular, have many specializations to deal with the daunting task of trying to digest enough cellulose to meet energy and nutrient needs. There are some bacteria living in the rumen of cattle and other similar herbivores, which can produce cellulase to break the cellulose present in the fodder into glucose molecules.

Nutrition in Microbes

Microorganisms include both autotrophic and heterotrophic organisms with respect to the mode of nutrition. The autotrophs include photosynthetic and chemosynthetic bacteria, and algae including cyanophyceae. The chemosynthetic bacteria use chemical energy for the synthesis of organic materials. Thus, they also belong to the producers of the ecosystem. The other bacteria, which form a greater part of the microbial population and all fungi, form the heterotrophs, which consume premade organic materials produced by plants. They live on the dead organic materials of plants and animals and are known as saprophytes. They secrete a number of enzymes to the substrate, the surface on which they grow. These enzymes digest the organic materials present on the substrate into simpler forms.


Movement is an important characteristic of living things. Animals are able to move from one place to another. But plants are restricted to some types of movements induced by water currents, turbidity, osmosis, etc. Animals are able to move because of the presence of contractile muscle fibers. Prokaryotes and other single-celled eukaryotic organisms move by hair-like structures called flagella and cilia or parts of pro top lasts (pseudopodia) as in the case of amoeba.

Amoeboid Movement

This type of movement is observed in some single-celled eukaryotes such as amoebas, slime molds, and eukaryotic cells such as lymphocytes of humans. Amoebas move by means of pseudopods (a foot-like extension at the front of a cell) attaching and detaching from the substratum. Locomotion may be correlated with the forward flow of fluid cytoplasm (endoplasm) into advancing pseudopodia through a surrounding gel-like ectoplasmic tube. The ectoplasm forms at the pseudopodia tip in a region called the fountain zone. As the amoeba advances, the ectoplasmic tube "liquefies" at the posterior end to form endoplasm. As the cell moves, new pseudopodia are formed in the direction of movement while the earlier ones are withdrawn. Amoeboid movement has a striking similarity with cytoplasmic movement known as cyclosis. The cytoplasmic streaming movement is a common characteristic of all plant and animal cells. This has an important role in intracellular transport. The cytoplasmic streaming movement and amoeboid movement by pseudopodia may be dependent on the contractile activity of protein fibers such as actin and myosin present in the cytoplasm along with the cytoskeleton.

Movement by Cilia and Flagella

Bacteria move using a rotating flagellum. Non-animal eukaryotes achieve motion in many ways, including moving by cilia and flagella, growing roots and hyphae, or dispersing gametes, spores, and seeds with the help ofwifd, water, and animals.

Cilia and flagella are the main locomotory organs (organelle) of prokaryotes such as bacteria and other single-celled organisms. Both flagella and cilia have identical internal structures. Microtubules form the internal structures of both cilia and flagella. They are also involved in other cellular movements such as movement of chromosomes and streaming movement of protoplasts, etc. The combined stroking movement of cilia propels certain unicellular organisms, such as paramecia, through their environment and moves fluid and particles over the surface of ciliated cells of higher eukaryotes. Flagella provide the propulsion for motile cells ranging from bacteria to sperm of higher eukaryotes. The main difference between cilia and flagella is in their stroking pattern and also in their length and number per cell. Flagella beat with a symmetrical undulation that is propagated as a wave along entire length of flagella. Flagella are very long and less in number. Flagellated cells usually carry one or few flagella. Ciliated cells usually have thousands of cilia all over the cell surfaces and are very short. A cilium beats symmetrically· with a fast stroke in one direction followed by slower recovery stroke. Cilia and flagella are also present in many multicellular organisms. There are some types of tissues in higher organisms where cilia are present. For example, in mammals the ciliated epithelium helps in the transport of certain materials on the internal surfaces as in the case of the movement of mucus in the respiratory tract. The sperm of most animals move with help of single flagella.

Muscle and Movement

Even though all organisms can move directly or indirectly, the animals have an especially impressive range of movement. The presence of muscles contributes a special ability for animals in movement. The contraction of muscle tissue powers animal movement. Muscle contains thin filaments of the proteins actin and myosin; myosin filaments lie between the actin filaments within a sarcomere, the basic contractile unit of muscle. A series of sacromeres attached end-to-end makes up a single fiber called myofibrils. A number of myofibrils bundled together form a muscle fibril. Myofibrils are bundled to form a muscle fiber, which is further bundled to constitute a functional body muscle (e.g., the human biceps). Since muscles only produce force when contracting, they must work as opposing pairs to give the full range of possible motion.

Sarcomeres appear as bands under a microscope. Each sarcomere is bounded on either side by dark lines, the Z discs. The cells contain the contractile proteins, actin and myosiJ\, which are arranged in a very specific manner. Z discs form the anchor points for the actin filaments. From this point actin filaments extend toward the center of the sarcomere. Myosin filaments are present in between the actin filaments toward the middle.

Muscles contract as the actin and myosin filaments slide past one qnother. The filaments do not decrease in length during the process of contraction and relaxation. ATP binds to the myosin head at a specific binding site and releases myosin from the actin filament. Myosin hydrolyzes the ATP into ADP and Pi. (Note that myosin is an ATPase.) Some of the energy is used to change the position of the myosin from a "bent" low-energy state, to an "open" high-energy state. Energized myosin binds to a site on the actin filament. ADP and Pi are released from the myosin head, and this causes the head to "spring back" to its original bent configuration moving the actin filament toward the sarcomere center, pulling the Z discs inward causing contraction of the muscle. The muscles are anchored to the skeleton for exerting the force caused by the contraction. Following contraction, the muscle fibers return to their original position.

Muscle strength is increased somewhat by stretching existing muscle cells through exercise, but mostly by increasing the number of muscle cells. In contrast, muscle speed is mainly influenced by muscle length and the percentage of fast or slow muscle fibers.

Muscles and skeleton work together to control the strength and speed of animal movement. The physical model of a lever system explains how vertebrate skeleton and muscles interact to achieve adaptive movement.

Animals move by swimming, running, or flying, with all three requiring the production of thrust. Environmental drag, caused by friction with the surrounding molecules and the pressure of those molecules sticking to the body, resists thrust, and thereby restricts animal's motion. Natural selection has favored organisms that minimize drag.

Cell Communication and Signal Transduction Pathways

The cells, unicellular or multicellular, respond to changes in the environment. In multicellular organisms, cells communicate with the neighboring cell in order to coordinate the functions of the system and body. Cell-to-cell communication is essential for normal functioning of multicellular organisms, and this is because they carry special abilities to maintain a well-defined communication network. In recent past, "cell signaling" has become a fascinating field. It explains a lot of critical issues regarding embryological development, hormone action, and the development of diseases such as cancer.

Cell Communication

Cell-to-cell communication is essential for multicellular organisms for coordinating various metabolic activities including activation of immune systems and gene expression. Interestingly, the same fundamental cell communication strategies are evident in many different types of cells. The cell-to-cell communication usually occurs through certain chemicals called as signal molecules. Signal molecules are small organic molecules, which can interact with certain specific proteins known as receptors. The signal molecules can be an amino-acid-like tyrosine and its derivatives or small peptides such as insulin or steroid hormones and growth regulators such as cytokines. Certain environmental factors also can impart some signals, which can be received by some receptor proteins. Signals that originate from environmental factors include temperature, electromagnetic waves of different spectrum such as visible light, osmolarity, ions such as iron, etc. Recipient cells, which receive these signals through receptors, are located on the surface of the cell membranes. Then the cells can respond to these signals by accepting them or by transmitting them to the next target molecule or cells.

Communicating cells may be close together or far apart: There are local regulators that influence cells in the more immediate vicinity. Growth factors are examples of local regulators that stimulate nearby cells to grow and multiply.

Paracrine signaling is another local signaling in animals. When a nerve cell produces a chemical signal, called a neurotransmitter, that diffuses to a single target cell that is very close to the first cell. This is known as synaptic signaling. Local signaling in plants is not well understood, although we do know that they must use different mechanisms since they have cell walls. In both animals and plants, hormones are used for cell signaling at greater distances. In endocrine (hormone) signaling, the specialized cells release hormone molecules into the circulatory system that then carry the hormones to the target cells in other parts of the body.

Cells may also communicate by direct contact. Cell junctions provide cytoplasmic continuity between cells and signaling substances in one cell can therefore diffuse into the cytoplasm of the adjacent cell.

Signal Transduction

There are three stages in the process of cell signaling or communication:

1. Reception-a protein at the cell surface detects chemical signals.

2. Transduction-a change in protein stimulates other changes including signal-transduction pathways.

3. Response-almost any cellular activity.

Once the target cell receives the signal molecule it converts the signal to a form that can bring about a specific cellular response. This often occurs in a series of steps called a signal transduction pathway. Signal molecules bind to receptor protein, in cell membranes, and generally cause a conformational change in the proteins. This change in conformation is transmitted to the cytoplasmic domain or part of the receptor molecule. The transformed molecule interacts with the information-relaying molecules in the cytoplasm. These molecules are small molecules present in the cytoplasm known as secondary messengers. Calcium ions and Cyclic AMP (cAMP) are examples. This further starts a series of chain reactions, which ultimately reaches the target gene and causes its expression or repression. A single cell may have several types of receptors each binding to a specific signal molecule. A cell can receive a number of different types of signal molecules simultaneously. Once the signals are relayed into the cells, they are selectively routed through various signal pathways to the target, which may be a gene or a protein. Usually the cellular response for a signal molecule may be a change in gene expression, change in ion permeability, or a change in the enzyme activity or protein three-dimensional structure, which ultimately affects the metabolism of the cell or organism.

Some types of signal molecules pass through the cell membrane and directly activate the gene or proteins, without the involvement of any secondary messengers. Lipid-soluble molecules such as steroids (steroid hormones) or small molecules (such as nitric oxide) are examples. Molecules such as interferon and interleukin can also do the same type of direct activation of a gene. Through cell-to-cell signaling and signal transduction, the information that the cells acquire from the environment and from other neighboring cells is effectively monitored and responded into the appropriate manner.

The Important Steps in the Cell Cycle

A rising level of G1 cyelins signals the cell to prepare the chromosomes for replication. A rising level of S-phase promoting factor (SPF) prepares the cell to enter S-.phase and duplicate its DNA (and its centrioles). As DNA replication continues, one of the cyclins shared by G1 and S-phase CDKs (cyclin E) is destroyed and the level of mitotic cyclins begins to rise (in G2).

M-phase promoting factor (the complex of mitotic cyclins with M-phase CDK) initiates the assembly of the mitotic spindle, breakdown of the nuclear envelope, and condensation of the chromosomes.

These events take the cell to the metaphase of mitosis.

At this point, the M-phase promoting factor activates the anaphase promoting complex (APC), which allows the sister chromatids at the metaphase plate to separate and move to the poles (= anaphase), completing mitosis: It destroys the M-phase cyclins. It also turns on synthesis of G1 cyclins for the next turn of the cycle and degrades geminin, a protein that has kept the freshly-synthesized DNA in S-phase from being re-replicated before mitosis.

Checkpoints: Quality Control of the Cell Cycle

The cell has several systems for interrupting the cell cycle if something goes wrong. There are some points in the cell cycle where the cell can check the sequence of activities related to its replication. These points are known as checkpoints. The following are the important checkpoints in the cell cycle, which monitor the healthy progress of cell division:
DNA damage checkpoints:

These sense DNA damage before the cell enters S-phase (a G1 checkpoint), during S-phase, and after DNA replication (a Gz checkpoint). The cell seems to monitor the presence of okazaki fragments on the lagging strand during DNA replication. The cell is not permitted to proceed in the cell cycle until these have disappeared.

Spindle checkpoints:

These are the final checkpoints also known as M-phase checkpoints. They detect any failure of spindle fibers to attach to kinetochores and arrest the cell in metaphase (M checkpoint). They monitor the alignment and detect improper alignment of the spindle itself and block cytokinesis. If the damage caused to the DNA is irreparable, it triggers the process of apoptosis or cell death.

All the checkpoints examined require the services of a complex of proteins. Mutations in the genes encoding have been associated with cancer; that is, they are oncogenes. This should not be surprising since checkpoint failures allow the cell to continue dividing despite damage to its integrity.

Thursday, December 25, 2008



A eukaryotic cell undergoes alternate phases of division and non-division. The sequences of events occurring from the completion of one division to the next division form one cell cycle. The stage, or the interval, between two consecutive mitotic divisions is the interphase. Therefore, a cell cycle can be considered as interphase + mitosis. The interphase is metabolically very dynamic and is further divided into S-phase, Gl, and G2 phase. The period between M-phase and S-phase is called G1; that between S and M is G2. A cell cannot divide into two, the two into four, etc., unless two processes alternate: doubling of its genome (DNA) in S-phase (synthesis phase) of the cell cycle and halving of that genome during mitosis (M-phase).

Stages of Cell Growth:

1. G1 phase: primary growth phase. Cell does its housekeeping activities. 
2. S-phase: DNA replication. 
3. G2 phase: chromosome condensation, cell organelle replication. 
4. M-phase: mitosis (nuclear division) (prophase, metaphase, anaphase, and telophase). 
5. C phase: cytokinesis (cytoplasmic division), daughter cells form.

Interphase is the longest stage of the cell cycle. Human cells contain 46 chromosomes during the Gl stage of interphase. This is doubled to 92 during the S stage of interphase. 

A typical cell takes about 16 hours to complete the cell cycle. The actual process of cell division or mitosis occupies only a small part of this cycle, approximately one hour. The lengths of Sand G2 are almost equal in all cell types, but the length of the Gl phase varies considerably between cells.

Normally the cells at G1 phase can follow either of the two paths. The cell after the cell division may withdraw from the cell cycle and enter into a resting phase called the Go phase, or it can enter into the G1 phase of the cell cycle. Cells in the Go phase are viable and metabolically active but can be stimulated to enter into the G1 phase at any time and start the cell cycle again. Often, Go cells are terminally differentiated: they will never re-enter the cell cycle but instead will carry out their function in the organism until they die.

For other cells, Go can be followed by re-entry into the cell cycle. Most of the lymphocytes in human blood are in Go. However, with proper stimulation, such as encountering the appropriate antigen, they can be stimulated to re-enter the cell cycle (at G1) and proceed onto new rounds of alternating S phases and mitosis. Go represents not simply the absence of signals for mitosis but an active repression of the genes needed for mitosis. Cancer cells cannot enter Go and are destined to repeat the cell cycle indefinitely. 

Regulation of the Cell Cycle

The cell cycles in almost all eukaryotic cells are essentially the same with minor variations in the duration of each phase. There are some proteins in the cytoplasm that control and coordinate the passage of a cell in the correct order through the cell cycle. The major proteins involved in the regulation are called cyelins. There are three groups:

G1 cyelins S-
phase cyelins M-
phase cyelins

The levels of these cyclins in the cell rise and fall with the stages of the cell cycle. The group of enzymes, Cyelin-dependent kinase (CDKs), phosphorylate cyclins. Again, there are three groups of CDKs:

S-phase CDKs M-
phase CDKs

Their levels in the cell remain fairly stable, but each must bind to the appropriate cyclin in order to be activated. The levels of cyclins always fluctuate in the cells. The CDKs add phosphate groups to a variety of protein substrates that control processes in the cell cycle.

The third group of proteins involved in the regulation of cell cycle is anaphase-promoting complex (APC) and other proteolytic enzymes. The APC triggers the events leading to destruction of the cohesin (a protein that joins the sister chromatids), thus allowing the sister chromatids to separate. It also degrades the mitotic (M-phase) cyclins. 

Saturday, December 20, 2008

Cell Division

Cell division is an integral part of the process of reproduction, growth, and repair of the body. During cell division, genetic material is distributed among the daughter cells. This is the important phenomenon taking place during all types of cell divisions. There are two types of cell division observed in eukaryotic cells. They are mitosis and meiosis. The distribution of genetic materials among the daughter cells is so important because their future development and generation of cells developing from that will be entirely dependent on the genetic material that they receive from the parent cell. Mitosis is the cell division that occurs in the somatic cells (body cells) and meiosis takes place in the sex organs for the production of gametes. The main features and the process of mitosis and meiosis are discussed below.


Mitosis is the process that facilitates the equal partitioning of replicated chromosomes into two identical groups. Two new daughter cells arise from one original cell. All the cells created through mitosis are genetically identical to one another and to the cell from which they came. The main purpose of mitosis in eukaryotic cells is:
  • Growth of the individual,
  • To repair tissue, and
  • To reproduce asexually.
Mitosis is a nuclear division in which the daughter cells receive the same number of chromosomes as that of the parent cell. The nuclear division is sometimes referred to as karyokinesis, which is followed by the cytoplasmic division known as cytokinesis. The daughter cells resulting from mitosis are identical to each other and also to the parent cell in the quantity and quality of genetic material. The genetic information, which the cell is copying and distributing during mitosis, is contained in the form of chromosomes.

The period between two successive cell divisions is referred to as the interphase.It is not a part of mitosis, but forms the preparatory stage for cell division. The main metabolic activities during this stage of cell are respiration, protein synthesis, and the duplication of genetic material (DNA replication). Cells usually are small with no large vacuoles.

The interphase stage is subdivided into three parts: Gl, S, and G2. In the Gl stage, the cell carries out its "housekeeping" functions while it collects the materials it will need to divide. S stands for DNA synthesis and this is the stage in which the DNA makes a copy of itself. An enzyme (DNA polymerase) assists each DNA double helix in making a copy of it in a process known as DNA replication. The two identical DNA double helices are represented in the chromosomes as the sister chromatids, and they are held together by the centromere, which is visible as a constricted area somewhere along the length of the chromosome. The G2 stage of mitosis comes next, and in this stage the cell checks to see that everything is ready to begin mitosis. When the cell has duplicated its DNA and checked it to make sure that there are no errors, it is ready to begin the distribution of the DNA to two separate cells.

Mitosis is divided into four stages-prophase, metaphase, anaphase, and telophase. The important changes that the cells undergo in each phase are described below.


During prophase the nuclear membrane and nucleolus disappear. The chromosomes themselves condense from long, thin filaments into compact rods so that they can be more easily moved. The apparatus needed to move the chromosomes around is set up. In animal cells this is done by the two centrioles, which move toward opposite poles of the cell and begin to form the mitotic spindle. Plant cells do not have centrioles; they use a different mechanism to form the spindle fibers. Each chromosome has a spindle fiber attached to it at the centromere and extending off to either side of the cell where the centrioles are located. These spindle fibers are exerting tension on the chromosomes and when the centromere splits later on, this will allow the chromosomes to be pulled to either end of the cell.


Metaphase is an easy stage to recognize because all of the chromosomes are lined up at the equator of the cell. Depending on where the viewer is "standing," it can look as though the chromosomes are lined up east to west or it can look as though the chromosomes are aligned north to south.


In anaphase the centromere on each chromosome splits. Because the spindle fibers are exerting tension on the chromosomes, when the centromere splits each chromatid is pulled toward the spindle pole that it faces. Once a chromatid has its own centromere it can be called a chromosome.


In telophase the chromosomes reach the opposite poles of the cell and their attached spindle fibers disappear. A new nuclear envelope forms, the nucleolus reappears, and the condensed chromosomes expand once more. The cytoplasm divides in a process called cytokinesis, and this forms the two daughter cells. In animal cells the cell membrane pinches in from either side by a constriction and separates into two. In a plant, a new cell wall begins to form in the middle of the cell and gradually grows longer from each end as it works its way toward the edges of the cell.

Mitosis is finished and there now are two cells, which are identical to each other, and identical to the cell from which they came.

Microorganisms and Fermentation

Although baking bread, brewing beer and making cheese and making cheese has been going on for centuries, the scientific study of these biochemical processes is less than 200 years old. Clues to understanding fermentation emerged in the seventeenth century when Dutch experimentalist Anton Van Leeuwenhoek discovered microorganisms using his microscope. He unraveled the chemical basis of the process of fermentation using analytical techniques for the estimation of carbon dioxide. Two centuries later, in 1857, a French scientist Louis Pasteur published his first report on lactic acid formation from sugar by fermentation. He published a detailed report on alcohol fermentation later in 1860. In this report, he revealed some of the complex physiological processes that happen during fermentation. He proved that fermentation is the consequence of anaerobic life and identified three types of fermentation.
  • Fermentation which generates gas.
  • Fermentation that results in alcohol.
  • Fermentation which results in acids.
At the end of the nineteenth century, Eduard Buchner observed the formation of ethanol and carbon dioxide when cell-free extract of yeast was added to an aqueous solution of sugars. Thus, he proved that cells are not essential for the fermentation process and the components responsible for the process are dissolved in the extract. He named that substance ‘Zymase’. The fermentation process was modified in Germany during World War I to produce glycerine for making the explosive nitroglycerine. Similarly, military armament programs discovered new technologies in food and chemical industries which helped them win battles in the First World War. For example, they used the bacteria that converts corn or molasses into acetone for making the explosive cordite. While biotechnology helped kill soldiers, it also cured them. Sir Alexander Fleming’s discovery of penicillin the first antibiotic, proved highly successful in treating wounded soldiers.

Friday, December 19, 2008

Introduction to Biotechnology


The term Biotechnology was used before the twientieth century for traditional activities such as making dairy products such as cheese and curd as well as bread, wine, beer etc. But none of these could be considered  biotechnology in the modern sense. Genetic alteration of organisms through selective breeding plant cloning by grafting etc do not fall under biotechnology. The process of fermentation for the preparation and manufacturing of products such as alcohol, beer, wine dairy products, various types of organic acids such as vinegar, citric acid, amino acids and vitamins can be called classical biotechnology or traditional biotechnology. Fermentation is the process by which living organisms.

Modern biotechnology is similar to classical biotechnology in utilizing living organisms. So what makes modern biotechnology modern? it is not modern in the sense of using various living organisms, but in the techniques for doing so. The introduction of a large number of new techniques has changed the face of classical biotechnology forever. These modern techniques, applied mainly to cells and molecules, make it possible to take advantage of the biological process in a very precise way. For example, genetic engineering has allowed us to transfer the property of a single gene from one organism to another. 

Definitions of Biotechnology:

There are several definitions of biotechnology. One simple definition is that it is the commercialization of cell and molecular biology. According to United States National Science Academy, biotechnology is the "controlled use of biotechnical agents like cells or cellular components for beneficial use". It covers both classical as well as modern biotechnology . More generally, biotechnology can be defined as "the use of living organisms, cells or cellular components for the production of compounds or precise genetic improvement of living things for the benefit of man".

Even though biotechnology has been in practice for thousands of years, the technological explosion of the twentieth century, in the various branches--physics, chemistry, engineering, computer applications and information technology--revolutionized the development of life sciences which ultimately resulted in the evolution of modern biotechnology. 

Supported by an array of biochemical, biophysical and molecular techniques besides engineering and information technology.. life scientists were able to develop new drugs, diagnostics, vaccines, food products, cosmetics and industrially useful chemicals. Genetically-altered crop plants, which can resist the stress of pests, diseases and environmental extremes were developed. New tools and techniques to extend the studies on genomics and proteomics, no only of man but other organisms were also developed. The involvement of information technology and internet in biotechnology particularly genomics and proteomics has given birth to a new branch in biotechnology--the science of bioinformatics and computational biology. The skills of biotechnology, like any other modern science are founded on the previous knowledge acquired through the ages. If one wants to understand biotechnology, one should also know the history of its development.

Saturday, December 6, 2008

The history of gene therapy

In the early 1970s, scientists proposed "gene surgery" for treating inherited diseases caused by faulty genes. The idea was to take out the disease-causing gene and surgically implant a gene that functioned properly. Although sound in theory, scientists, then and now, lack the biological knowledge or technical expertise needed to perform such a precise surgery in the human body.

However, in 1983, a group of scientists from Baylor College of Medicine in Houston, Texas, proposed that gene therapy could one day be a viable approach for treating Lesch-Nyhan disease, a rare neurological disorder. The scientists conducted experiments in which an enzyme-producing gene (a specific type of protein) for correcting the disease was injected into a group of cells for replication. The scientists theorized the cells could then be injected into people with Lesch-Nyhan disease, thus correcting the genetic defect that caused the disease.

As the science of genetics advanced throughout the 1980s, gene therapy gained an established foothold in the minds of medical scientists as a promising approach to treatments for specific diseases. One of the major reasons for the growth of gene therapy was scientists' increasing ability to identify the specific genetic malfunctions that caused inherited diseases. Interest grew as further studies of DNA and chromosomes (where genes reside) showed that specific genetic abnormalities in one or more genes occurred in successive generations of certain family members who suffered from diseases like intestinal cancer, bipolar disorder, Alzheimer's disease, heart disease, diabetes, and many more. Although the genes may not be the only cause of the disease in all cases, they may make certain individuals more susceptible to developing the disease because of environmental influences, like smoking, pollution, and stress. In fact, some scientists theorize that all diseases may have a genetic component.

On September 14, 1990, a four-year old girl suffering from a genetic disorder that prevented her body from producing a crucial enzyme became the first person to undergo gene therapy in the United States. Because her body could not produce adenosine deaminase (ADA), she had a weakened immune system, making her extremely susceptible to severe, life-threatening infections. W. French Anderson and colleagues at the National Institutes of Health's Clinical Center in Bethesda, Maryland, took white blood cells (which are crucial to proper immune system functioning) from the girl, inserted ADA producing genes into them, and then transfused the cells back into the patient. Although the young girl continued to show an increased ability to produce ADA, debate arose as to whether the improvement resulted from the gene therapy or from an additional drug treatment she received.

Nevertheless, a new era of gene therapy began as more and more scientists sought to conduct clinical trial (testing in humans) research in this area. In that same year, gene therapy was tested on patients suffering from melanoma (skin cancer). The goal was to help them produce antibodies (disease fighting substances in the immune system) to battle the cancer.

These experiments have spawned an ever growing number of attempts at gene therapies designed to perform a variety of functions in the body. For example, a gene therapy for cystic fibrosis aims to supply a gene that alters cells, enabling them to produce a specific protein to battle the disease. Another approach was used for brain cancer patients, in which the inserted gene was designed to make the cancer cells more likely to respond to drug treatment. Another gene therapy approach for patients suffering from artery blockage, which can lead to strokes, induces the growth of new blood vessels near clogged arteries, thus ensuring normal blood circulation.

Currently, there are a host of new gene therapy agents in clinical trials. In the United States, both nucleic acid based (in vivo) treatments and cell-based (ex vivo) treatments are being investigated. Nucleic acid based gene therapy uses vectors (like viruses) to deliver modified genes to target cells. Cell-based gene therapy techniques remove cells from the patient in order to genetically alter them then reintroduce them to the patient's body. Presently, gene therapies for the following diseases are being developed: cystic fibrosis (using adenoviral vector), HIV infection (cell-based), malignant melanoma (cell-based), Duchenne muscular dystrophy (cell-based), hemophilia B (cell-based), kidney cancer (cell-based), Gaucher's Disease (retroviral vector), breast cancer (retroviral vector), and lung cancer (retroviral vector). When a cell or individual is treated using gene therapy and successful incorporation of engineered genes has occurred, the cell or individual is said to be transgenic.

The medical establishment's contribution to transgenic research has been supported by increased government funding. In 1991, the U.S. government provided $58 million for gene therapy research, with increases in funding of $15-40 million dollars a year over the following four years. With fierce competition over the promise of societal benefit in addition to huge profits, large pharmaceutical corporations have moved to the forefront of transgenic research. In an effort to be first in developing new therapies, and armed with billions of dollars of research funds, such corporations are making impressive strides toward making gene therapy a viable reality in the treatment of once elusive diseases

Chromosome elimination in Hemiptera

Chromosome elimination is a frequent occurrence in Hemiptera; one of the most interesting cases is that of Sciara. In Sciara coprophila the zygote carries the x chromosomes, one contributed by the egg and two by the spermatozoon (this results from an equational non dis-junction of the maternally derived x chromosome at the second meiotic division in the male following the selective elimination of paternal homologues at the first spermatocyte division). During early cleavage both paternal x chromosomes are eliminated from the somatic cell line of the males while only one is eliminated in the female. In the germ link one paternal x chromosome is eliminated both in the female and in the male, but not until the germ cells have reached their final destination in the gonad. Chromosome elimination may be thought of as a primitive, and in fact crude mechanism of "gene silencing" to be replaced by more subtle devices in the course of evolution. The eliminated chromosomes, or parts of chromosomes, or parts of chromosomes, contain the sexuality genes.

-> Cross section through the pharynx of Ascaris

Each cell line is committed to a certain number of DNA replication cycles before expressing its specific phenotype: in other words "the program for cell division is a part of the differentiative program of each cell line". We can derive that from a study of development of marine invertebrates. The Ascidian embryo offers unique opportunities to study cell lineage. Indeed, it shows the segregation of the major organ-forming territories occurs before the first cleavage.

Fertilized Ascidian Egg

Segration of Cell lines in the Embryo

In all multi cellular organism, the cleavage of the egg gives rise to cells which differ from one another and which, through successive cell divisions, will eventually give rise to homogeneous Cell populations (cell lines) each endowed with its own specific developmental program. This not only implies a process of sorting out of molecules (either pre-existing in the egg before fertilization or being synthesized in the course of development) into the various blastomers; but also of cells recognizing one another and coordinating their movements, their rate of cleavage, their metabolic activities, and the like.

The dichotomy between the two cell lines involves:

a) That in the somatic cell line, the genes which in the unicellular organism code for the surface structures responsible for the recognition of and interaction between cells of the two gametic types, are silenced. The evidence for this is indirect. The formation of mouse chimaeras shows that genetically male and female embryonic cells do not discriminate one another as different. Also, hybrid hystotypic aggregates can be formed in culture from such species as far as apart as chick and mouse. However, the possibility should be taken into consideration that in vitro conditions may alter the organization of the cell surface in such a way that some of its properties such as the species-specificity are lost while the tissue-specificity is retained. These observations are compatible with the view that the structures discriminating between male and female are not expressed at the surface of these cells.

b) The retention of a largely depressed genome by the cells of the germ line. This is inferred from the fact that in the oocyte, the complexity of the transcripts is several-fold greater than in the somatic cells. But there is no such direct evidence in the case of the male germ cells, it has been shown that at least in Drosophila, spermatocytes exhibit lampbrush chromosomes comparable to those of the oocyte.

The emergence of multicellular organism has required the establishment of cell junctions; not only as a means of holding the cells together, but as a vehicle of functional coordination between cells.

A classical example of a very precocious segregation of the somatic from the germ line is that of Ascaris. In this nematode while the lineage cells of the germ line retain their full chromosomes complement, in the cells of the somatic line pieces of chromosomes are lost; the loss amounts to about 27% of the total DNA of the cell. Interestingly, about one-half of the eliminated DNA consists of repetitive sequences and the other half of unique sequences.

First Human Gene Therapy

On September 14, 1990 at the U.S. National Institutes of Health W. French Anderson, M.D., and his colleagues R. Michael Blaese, M.D., C. Bouzaid, M.D., and Kenneth Culver, M.D., performed the first approved gene therapy procedure on four-year old Ashanthi DeSilva. Born with a rare genetic disease called severe combined immunodeficiency (SCID), she lacked a healthy immune system, and was vulnerable to every passing germ or infection. Children with this illness usually develop overwhelming infections and rarely survive to adulthood; a common childhood illness like chickenpox is life-threatening. Ashanthi led a cloistered existence -- avoiding contact with people outside her family, remaining in the sterile environment of her home, and battling frequent illnesses with massive amounts of antibiotics.

In Ashanthi's gene therapy procedure, doctors removed white blood cells from the child's body, let the cells grow in the lab, inserted the missing gene into the cells, and then infused the genetically modified blood cells back into the patient's bloodstream. Laboratory tests have shown that the therapy strengthened Ashanthi's immune system by 40%; she no longer has recurrent colds, she has been allowed to attend school, and she was immunized against whooping cough. This procedure was not a cure; the white blood cells treated genetically only work for a few months, after which the process must be repeated (VII, Thompson [First] 1993). As of early 2007, she was still in good health, and she was attending college. However, there is no consensus on what portion of her improvement should be attributed to gene therapy versus other treatments. Some would state that the case is of great importance despite its indefinite results, if only because it demonstrated that gene therapy could be practically attempted without adverse consequences.

Although this simplified explanation of a gene therapy procedure sounds like a happy ending, it is little more than an optimistic first chapter in a long story; the road to the first approved gene therapy procedure was rocky and fraught with controversy. The biology of human gene therapy is very complex, and there are many techniques that still need to be developed and diseases that need to be understood more fully before gene therapy can be used appropriately. The public policy debate surrounding the possible use of genetically engineered material in human subjects has been equally complex. Major participants in the debate have come from the fields of biology, government, law, medicine, philosophy, politics, and religion, each bringing different views to the discussion.

Genetic Engineering

Genetic engineering, genetic modification (GM) and gene splicing are terms for the process of manipulating genes, usually outside the organism's natural reproductive process.

It involves the isolation, manipulation and reintroduction of DNA into cells or model organisms, usually to express a protein. The aim is to introduce new characteristics or attributes physiologically or physically, such as making a crop resistant to a herbicide, introducing a novel trait, or producing a new protein or enzyme, along with altering the organism to produce more of certain traits.

Examples can include the production of human insulin through the use of modified bacteria, the production of erythropoietin in Chinese Hamster Ovary cells, and the production of new types of experimental mice such as the OncoMouse (cancer mouse) for research, through genetic redesign.

Since a protein is specified by a segment of DNA called a gene, future versions of that protein can be modified by changing the gene's underlying DNA. One way to do this is to isolate the piece of DNA containing the gene, precisely cut the gene out, and then reintroduce (splice) the gene into a different DNA segment.

Since a protein is specified by a segment of DNA called a gene, future versions of that protein can be modified by changing the gene's underlying DNA. One way to do this is to isolate the piece of DNA containing the gene, precisely cut the gene out, and then reintroduce (splice) the gene into a different DNA segment. Daniel Nathans and Hamilton Smith received the 1978 Nobel Prize in physiology or medicine for their isolation of restriction endonucleases, which are able to cut DNA at specific sites. Together with ligase, which can join fragments of DNA together, restriction enzymes formed the initial basis of recombinant DNA technology.

RNA Genes

RNA genes (sometimes referred to as non-coding RNA or small RNA) are genes that encode RNA that is not translated into a protein. The most prominent examples of RNA genes are transfer RNA (tRNA) and ribosomal RNA (rRNA), both of which are involved in the process of translation. However, since the late 1990s, many new RNA genes have been found, and thus RNA genes may play a much more significant role than previously thought. In the late 1990s and early 2000, there has been persistent evidence of more complex transcription occurring in mammalian cells (and possibly others). This could point towards a more widespread use of RNA in biology, particularly in gene regulation. A particular class of non-coding RNA, micro RNA, has been found in many metazoans (from Caenorhabditis elegans to Homo sapiens) and clearly plays an important role in regulating other genes. First proposed in 2004 by Rassoulzadegan and published in Nature 2006,
RNA is implicated as being part of the germline. If confirmed, this result would significantly alter the present understanding of genetics and lead to many question on DNA-RNA roles and interactions.RNA Deatiles,ScienceRibonucleic acid (RNA) is a nucleic acid polymer consisting of nucleotide monomers, that acts as a messenger between DNA and ribosomes, and that is also responsible for making proteins out of amino acids. RNA polynucleotides contain ribose sugars and predominantly uracil unlike deoxyribonucleic acid (DNA), which contains deoxyribose and predominantly thymine. It is transcribed (synthesized) from DNA by enzymes called RNA polymerases and further processed by other enzymes.
RNA serves as the template for translation of genes into proteins, transferring amino acids to the ribosome to form proteins, and also translating the transcript into proteins. Nucleic acids were discovered in 1868 (some sources indicate 1869) by Johann Friedrich Miescher (1844-1895), who called the material 'nuclein' since it was found in the nucleus. It was later discovered that prokaryotic cells, which do not have a nucleus, also contain nucleic acids. The role of RNA in protein synthesis had been suspected since 1939, based on experiments carried out by Torbjörn Caspersson, Jean Brachet and Jack Schultz. Hubert Chantrenne elucidated the messenger role played by RNA in the synthesis of proteins in ribosome.
The sequence of the 77 nucleotides of a yeast RNA was found by Robert W. Holley in 1964, winning Holley the 1968 Nobel Prize for Medicine. In 1976, Walter Fiers and his team at the University of Ghent determined the complete nucleotide sequenceDNA Bases Bio TechnologyDeoxyribonucleic acid, or DNA is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all living organisms. The main role of DNA is the long-term storage of information and it is often compared to a set of blueprints, since DNA contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information. Chemically, DNA is a long polymer of simple units called nucleotides, which are held together by a backbone made of alternating sugars and phosphate groups. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription. Most of these RNA molecules are used to synthesize proteins, but others are used directly in structures such as ribosomes and spliceosomes. Within cells,
DNA is organized into structures called chromosomes and the set of chromosomes within a cell make up a genome. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms such as animals, plants, and fungi store their DNA inside the cell nucleus, while in prokaryotes such as bacteria it is found in the cell's cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA, which helps control its interactions with other proteins and thereby control which genes are transcribed Biotechnology Indroduction. The convention recognized for the first time in international law that the conservation of biological diversity is "a common concern of humankind" and is an integral part of the development process.
The agreement covers all ecosystems, species, and genetic resources. It links traditional conservation efforts to the economic goal of using biological resources sustainably. It sets principles for the fair and equitable sharing of the benefits arising from the use of genetic resources, notably those destined for commercial use. It also covers the rapidly expanding field of biotechnology through its Cartagena Protocol on Biosafety, addressing technology development and transfer, benefit-sharing and biosafety issues. Importantly, the Convention is legally binding; countries that join it('Parties') are obliged to implement its provisions .
Apply Bio Technology Science The convention reminds decision-makers that natural resources are not infinite and sets out a philosophy of sustainable use. While past conservation efforts were aimed at protecting particular species and habitats, the Convention recognizes that ecosystems, species and genes must be used for the benefit of humans. However, this should be done in a way and at a rate that does not lead to the long-term decline of biological diversity The convention also offers decision-makers guidance based on the precautionary principle that where there is a threat of significant reduction or loss of biological diversity, lack of full scientific certainty should not be used as a reason for postponing measures to avoid or minimize such a threat. The Convention acknowledges that substantial investments are required to conserve biological diversity. It argues, however, that conservation will bring us significant environmental, economic and social benefits in return.In this situation, your range of choices is very broad and many packages will meet these limited.