Monday, January 26, 2009

Know the process of Karyotyping

Karyotyping is a valuable research tool used to determine the chromosome complement within somatic or cultured cells. It is important to keep in mind that karyotypes evolve with organisms. Because of this evolution, it is important for the interpretation of biochemical or other data, that the karyotype of a specific subline be determined. Many morphological and physiological problems can be traced to the change in the karyotype. Numerous technical procedures have been reported that produce banding patterns on metaphase chromosomes. A band is defined as that part of a chromosome, which is clearly distinguishable from its adjacent segments by appearing darker or lighter. The chromosomes are visualized as consisting of a continuous series of light and dark bands. A G-staining method resulting in G-bands uses a Giemsa dye mixture or Leishman dye mixture as the staining agent.

Karyotypes are usually prepared from cells in which chromosomes can be readily distinguished, counted, and measured. Chromosomes at the mitotic metaphase, meiotic metaphase II, and pachytene of meiosis are best suited to make and evaluate the karyotypes. After taking the microphotograph of the complete chromosomes, a photograph karyotype may be prepared by cutting out the chromosomes from the microphotograph and arranging them in ordered pairs. A diagrammatic representation of karyotype is called an idiogram. It can be prepared by taking measurements and drawing the chromosomes with all their relative differences. An idiogram represents the diploid complement of chromosomes. It shows the number, size, and shape and allows easy comparison of chromosomes within the karyotype and also with other organisms.

The position of the centromere with respect to the length of arms is called arm ratio of the chromosomes.

Karyotyping is often used for the parental diagnosis and detection of variations in the chromosome number and structure, aberrations, and anomalies, which are the common cause of many congenital defects and spontaneous abortions.

Tags: Bio Technology, Bio Genetics, Karyotyping

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