To me, it is a paradigm of the decline and fall of the Y chromosome
," says reproductive biologist Jennifer Marshall Graves of La Trobe University in Melbourne, Australia.
The UC Berkeley researchers demonstrated that if fewer males were the only cause of the low variability, it would mean that fewer than 1 in 4 males throughout history had passed on their Y chromosome
SRY is the gene on the mammalian Y chromosome
that determines that the organism will be male.
He was determined to prove, through variation in the Y chromosome
, that more than three stallions - the Byerley Turk, Darley Arabian and Godolphin Arabian - founded the breed.
Lell and his co-authors have recently refuted this single migration interpretation of Y chromosome
Using estimates of the mutation rate of microsatellite DNA, the investigators conclude that the first man to have this particular form of the Y chromosome
lived in Mongolia roughly 1,000 years ago.
A separate study of more than 8,500 men with cancer and more than 5,300 healthy men also found that Y chromosome
loss increases with age.
Members of his lab have dealt their fatal blow by sequencing the Y chromosome
of the rhesus macaque-an Old World monkey whose evolutionary path diverged from that of humans some 25 million years ago-and comparing it with the sequences of the human and chimpanzee Y chromosomes
A unique aspect of the Y chromosome
that lends itself to this sort of research is that the Y does not swap stretches of DNA with other chromosomes.
In contrast, the human Y chromosome
dates from 200 million to 320 million years ago.
Underhill studies pairs of mutations on the Y chromosome
in current populations.
Hammer of the University of Arizona in Tucson, analyzed a different set of international Y chromosome
data in 2001 and largely confirmed the evolutionary tree proposed by Underhill's group.
and his colleagues have identified a means by which the Y chromosome
may forestall, or at least delay, the gradual degradation that some biologists argue will ultimately delete it from the human genome.
Men from eastern Africa fell into a genetic group at the root of the Y chromosome
In at least eight species of the mouse genus Akodon, from 10 percent to 60 percent of the females carry a Y chromosome
in place of one of the two X chromosomes usually found in the cells of female mammals, report Hopi E.