[3][5] During his final year at Swarthmore, Page attended class just one day a week and spent the rest of his time researching chromatin structure in the laboratory of molecular biologist Robert Simpson at the National Institutes of Health.
Page found that he had misinterpreted his data because one of the XY females in his study had a second deletion at the site which proved to be the location of the real sex-determining gene.
Launching a second round of media attention, Nature published his findings together with a paper from the British group that identified the sex-determining gene, which they termed SRY.
[16] Page collaborated with a team at the Genome Institute at Washington University to make a complete map of the Y chromosome, which they achieved in 2003.
[19][20] The lab also found that aberrant crossing over within the Y chromosome's palindromes underlies a wide range of disorders of sexual differentiation, including Turner syndrome.
[3][21] In 1999, Page and his then-graduate student Bruce Lahn showed that the X and Y chromosomes had diverged in four steps, beginning 200-300 million years ago.
In one study, Page found that human X and mouse Y chromosomes have converged, independently acquiring and amplifying gene families expressed in testicular germ cells.