Editing David C. Page (section)

===Evolution of the Y chromosome===
With the development of more detailed maps of the Y chromosome, in the mid-1990s Page began to find genetic evidence confirming the theory that both the X and Y chromosomes had evolved from [[autosome]]s, beginning with the 1996 discovery that a family of genes called [[DAZ associated protein 1|DAZ]] (deleted in azoospermia) had been transposed from an autosome to the Y chromosome.<ref name=":0" /><ref>{{Cite journal|title = The DAZ gene cluster on the human Y chromosome arose from an autosomal gene that was transposed, repeatedly amplified and pruned|journal = Nature Genetics|date = 1996-11-01|issn = 1061-4036|pmid = 8896558|pages = 292–299|volume = 14|issue = 3|doi = 10.1038/ng1196-292|first1 = R.|last1 = Saxena|first2 = L. G.|last2 = Brown|first3 = T.|last3 = Hawkins|first4 = R. K.|last4 = Alagappan|first5 = H.|last5 = Skaletsky|first6 = M. P.|last6 = Reeve|first7 = R.|last7 = Reijo|first8 = S.|last8 = Rozen|first9 = M. B.|last9 = Dinulos|s2cid = 34964224}}</ref> 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.<ref>{{Cite journal|title = Four evolutionary strata on the human X chromosome|journal = Science|date = 1999-10-29|issn = 0036-8075|pmid = 10542153|pages = 964–967|volume = 286|issue = 5441|first1 = B. T.|last1 = Lahn|first2 = D. C.|last2 = Page|doi=10.1126/science.286.5441.964}}</ref> Later cross-species comparisons would show that while ancestral genes on the Y chromosome initially underwent rapid decay,<ref name=":3" /><ref>{{Cite journal|title = Convergent evolution of chicken Z and human X chromosomes by expansion and gene acquisition|journal = Nature|date = 2010-07-29|issn = 1476-4687|pmc = 2943333|pmid = 20622855|pages = 612–616|volume = 466|issue = 7306|doi = 10.1038/nature09172|first1 = Daniel W.|last1 = Bellott|first2 = Helen|last2 = Skaletsky|first3 = Tatyana|last3 = Pyntikova|first4 = Elaine R.|last4 = Mardis|first5 = Tina|last5 = Graves|first6 = Colin|last6 = Kremitzki|first7 = Laura G.|last7 = Brown|first8 = Steve|last8 = Rozen|first9 = Wesley C.|last9 = Warren|bibcode = 2010Natur.466..612B|url = http://dspace.mit.edu/bitstream/1721.1/66578/1/050610_Submitted.pdf}}</ref> the remaining genes have remained stable for the last 25 million years,<ref>{{Cite journal|title = Strict evolutionary conservation followed rapid gene loss on human and rhesus Y chromosomes|journal = Nature|date = 2012-03-01|issn = 0028-0836|pmc = 3292678|pmid = 22367542|pages = 82–86|volume = 483|issue = 7387|doi = 10.1038/nature10843|language = en|first1 = Jennifer F.|last1 = Hughes|first2 = Helen|last2 = Skaletsky|first3 = Laura G.|last3 = Brown|first4 = Tatyana|last4 = Pyntikova|first5 = Tina|last5 = Graves|first6 = Robert S.|last6 = Fulton|first7 = Shannon|last7 = Dugan|first8 = Yan|last8 = Ding|first9 = Christian J.|last9 = Buhay|bibcode = 2012Natur.483...82H}}</ref> overturning the long-held view that the Y chromosome was going extinct.<ref name=":0" /> In a 2014 study, Page concluded that the conserved genes on the Y chromosome played an important role in male viability, since they were dosage-dependent genes with similar but not identical counterparts on the X chromosome that all have regulatory roles in transcription, translation, and protein stability. Because these genes are expressed throughout the body, Page further concluded that these genes give rise to differences in the biochemistry of male and female tissues.<ref>{{Cite journal|title = Mammalian Y chromosomes retain widely expressed dosage-sensitive regulators|journal = Nature|date = 2014-04-24|issn = 0028-0836|pmc = 4139287|pmid = 24759411|pages = 494–499|volume = 508|issue = 7497|doi = 10.1038/nature13206|language = en|first1 = Daniel W.|last1 = Bellott|first2 = Jennifer F.|last2 = Hughes|first3 = Helen|last3 = Skaletsky|first4 = Laura G.|last4 = Brown|first5 = Tatyana|last5 = Pyntikova|first6 = Ting-Jan|last6 = Cho|first7 = Natalia|last7 = Koutseva|first8 = Sara|last8 = Zaghlul|first9 = Tina|last9 = Graves|bibcode = 2014Natur.508..494B}}</ref>

In super-resolution studies of the sex chromosomes, Page has found evidence of an evolutionary "arms race" between the X and Y chromosomes for transmission to the next generation. 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.<ref>{{Cite journal|title = Independent specialization of the human and mouse X chromosomes for the male germ line|journal = Nature Genetics|date = 2013-09-01|issn = 1061-4036|pmc = 3758364|pmid = 23872635|pages = 1083–1087|volume = 45|issue = 9|doi = 10.1038/ng.2705|language = en|first1 = Jacob L.|last1 = Mueller|first2 = Helen|last2 = Skaletsky|first3 = Laura G.|last3 = Brown|first4 = Sara|last4 = Zaghlul|first5 = Susan|last5 = Rock|first6 = Tina|last6 = Graves|first7 = Katherine|last7 = Auger|first8 = Wesley C.|last8 = Warren|first9 = Richard K.|last9 = Wilson}}</ref> Another study found that the mouse Y chromosome had acquired and massively amplified genes homologous to the testis-expressed gene families on the mouse X chromosome.<ref>{{Cite journal|title = Sequencing the mouse Y chromosome reveals convergent gene acquisition and amplification on both sex chromosomes|journal = Cell|date = 2014-11-06|issn = 1097-4172|pmc = 4260969|pmid = 25417157|pages = 800–813|volume = 159|issue = 4|doi = 10.1016/j.cell.2014.09.052|first1 = Y. Q. Shirleen|last1 = Soh|first2 = Jessica|last2 = Alföldi|first3 = Tatyana|last3 = Pyntikova|first4 = Laura G.|last4 = Brown|first5 = Tina|last5 = Graves|first6 = Patrick J.|last6 = Minx|first7 = Robert S.|last7 = Fulton|first8 = Colin|last8 = Kremitzki|first9 = Natalia|last9 = Koutseva}}</ref>