The grid you can see in this microarray slide is actually composed of 30,000 individual DNA dots, each targeted to match a specific human gene. In order to work out which genes are being expressed, messenger RNA is first extracted from the cell sample and copied back to DNA using an enzyme. This DNA, called cDNA, is complementary to the target gene, so we'll associate with it, or hybridize with it, on the slide. After labeling with a fluorescent dye, the cDNA is washed over the slide. The genes currently active in the cell can then be identified by the level of the fluorescence and the color of the spots.
Keywords:
dna microarray,target gene,messenger rna,gene analysis,human gene,genes,fluorescent dye,dots,large scale,animation
Special techniques are used for screening each individual’s genome for millions of different SNPs. This kind of comparison is referred to as a genome-wide association study.
Igor Dawid and Thomas Sargent explain how they developed subtractive mRNA hybrization to find genes expressed by different cell types. Pat Brown and Steve Fodor show how genomes can be screened with DNA arrays and GeneChips�
Jonathan Sebat, a researcher at Cold Spring Harbor Laboratory, discusses how association studies are used to determine the causes of genetic disorders.
The last step! A technician applies the label and serial number to a GeneChip cassette. The GeneChip is now ready to be used in a laboratory to perform large-scale genetic analysis.
Doctor Josh Dubnau explains that some genes are preferentially active in one part of the brain or body, while other genes are particular active in another location.
Professor David Lewis outlines how microarrays have transformed the search for schizophrenia genes and led to his group's discovery of the candidate gene, RGS4.