However, the questions of which alleles were key, how they worked together and in what combinations and why this system evolved were left unanswered, though tantalizing close. This compelled the current team of collaborators to step back to review what actually constitutes an allele.
"There has to be some segment of that gene that is responsible in this allelic series, where if you have two different coding sequences in that part of the gene you end up producing a female," said Page, who is also the Foundation Chair of Life Sciences at ASU. "So we asked how different do two alleles have to be? Can you be off one or two base pairs or does it always have to be the same set of sequences? We came up with a strategy to go in and look at these 18-20 alleles and find out what regions of these genes are responsible among these variants."
"In this process, we also had to determine if there are intermediate kinds of alleles and discover how they might have evolved," said Page.
What the authors found was that at least five amino acid differences can control allelic differences to create femaleness through the complementary sex determiner (csd) genethe control switch.
"We discovered that different amounts of arginine, serine and proline affect protein binding sites on the csd gene, which in turn lead to different conformational states, which then lead to functional changes i
|Contact: Margaret Coulombe|
Arizona State University