"By being able to see... all the genes, all the genetic variation, we can readily pick out answers."
Eric Lander, a human genome project leader
There are about 30,000 different genes in human DNA. Different cells in the body, although having identical DNA, switch on and off different genes, depending on what is needed to build that particular cell. Studying which genes are active in a cell is a useful way to find out what makes it function, and helps identify what has gone wrong when it is not functioning properly.
In 1989 U.S. scientist Stephen Fodor presented a technique that was to revolutionize DNA analysis. He created a DNA microarray—a glass slide with up to 500,000 different strands of DNA attached to it. When a gene is switched on in a cell, a complementary copy of that gene's information (called messenger ribonucleicacid, or mRNA) is produced by the cell. more...