Thursday, May 21, 2009

What is Transgenic Locus

Gene constructs used in genetic transformation posses a promoter, coding region, and termination sequence. In the vicillin promoter, specific for expression in seeds, drives the expression of the gene UDP 6-glucose dehydrogenase in the antisense orientation. The construct also possesses the NOS (noplaine synthase) termination sequence, which marks the site for the end of transcription. Besides the transgene of interest, in general, reporter genes are introduced simultaneously to facilitate the identification and selection of transformed individuals.

For the selection of the transformed cells, the gene construct contains a gene sequence that codes for antibiotic or herbicide resistance. Frequently, neomycin or hygromycin antibiotic resistance genes or the phosphinotricim acetyl transferase herbicide tolerance gene is included under a strong constitutive promoter, such as 35SCaMV. The transformed cells would be the only ones possessing the capability to grow in a medium with a selective agent (antibiotic or herbicide), thereby facilitating their selection.

Frequently, a gene reporter is also included in the genetic construction. The function of this reporter is to allow the visual identification of transformed cells. Three genes have been used as reporters in plant transformation: Glucaronidase (GUS), Luciferase (LUC) and Green Fluorescent Protein (GFP). GUS allows the identification of transformed individuals by the expression of a blue color, because they become blue in the presence of the chemicals X-Gal and IPTG (isopropyl beta D-thiogalactoside). Luciferase, a protein in fireflies, turns the transformed individuals phosphorescent, and GFP, isolated from a species of jellyfish, codes for a fluorescent-green color in transformed individuals.

Genetic transformation of individuals is a difficult task. The science behind the methods is understandable on a basic level, but the results from the procedures do not always work out as planned. Specific gene sequences are needed to induce the expression of a transgene, and genes are needed to identify the transformed cells. Still, the use of transformation is being improved to more accurately express desired traits in different organisms. The comprehension of the intricacies of transformation is a key to understanding the broad applications of biotechnology.

Tags: Bio Technology, Bio Genetics, Genetic Transformation

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