Cdna-basic concept

Cdna-basic concept

[link] Recently, several types of the DNA microarrays were introduced. Applications of microarrays range from the study of gene expression in yeast( Lashkari et al., 1997) under different environmental stress conditions to the comparison of gene expression profiles for tumors from cancer patients (Golub et al., 1999). The first approach is to use the chemically synthesized form of DNA called COMPLEMENTARY DNA (cDNA) , which contains only coding part of the sequence, complementary to its corresponding mRNA transcript. Microarrays have a form of microscope slides containing hundreds to thousands of immobilized DNA samples that are hybridized in a manner very similar to the Northern (Alwine et al., 1977)and Southern blot (Southern, 1975). The main function of a microarray is to detect the level of mRNA transcript of genes of interest. The plates are incubated in the solution containing genetic material under consideration. The mRNA transcripts floating in the solution would hybridize to their complementary cDNA, previously placed on the microarray chip. Since the cDNA on the chip is fluorescently labeled, every spot will emit a light in the ultraviolet environment, intensity of which depends on the amount of hybridized mRNA (Schena et al., 1995). The differentiation of the cDNA’s ultraviolet dye allows the comparison of the gene expression under different experimental conditions (case- control studies). The preparation of the microarray for case-control study is schematically depicted on Figure 1. Initial data obtained from DNA microarrays are in the form of scanned images. Coding the gene expression by means of colors can be helpful for building d genetic maps and graphical data processing. Expression gene map is presented in the form of a table; the rows of which corresponds to the consecutive genes and columns represent different samples, for example under multiple experimental conditions or for different patients. More informations available at: Bioconductors , follow link to training .