Studies in model organisms like yeast -- just as in humans -- have failed to detect a large fraction of the genes believed to underlie most complex traits. So Kruglyak and his team developed a method using a sample size of yeast that went beyond the scale of any human studies. They crossed two strains of yeast, generating about 10 million offspring. Each of these progeny was genetically distinct as opposed to being a clone.
To find a subset offspring that shared a trait, the scientists grew the progeny on a chemical that causes breaks in DNA, killing most of them. They then sequenced the genomes of the few thousand yeast that survived, looking to see what genes they inherited from each parent.
Mendel's laws, which explain the principles of heredity, state that most of the genetic material should be randomly inherited from one or the other parent in a manner equivalent to a coin flip --half of the cells should have one parent's genes and half the other parent's. But, at the locations of the genes that protect yeast from the chemical, most of the cells should have genetic material from the parent with the version of the gene that produces greater resistance.
The surviving yeast cells' genomes were placed on tiny chips and scanned on automated laboratory machines, a process known as genotyping. The machines surveyed each yeast cell's genome for strategically selected markers of genetic variation. They found certain genetic variations to be significantly more frequent in the surviving yeast, serving as a powerful pointer to the regions of the genome where the genes underlying the tra
|Contact: Kitta MacPherson|