May 22, 2021 09:06 PM
https://www.sciencealert.com/voles-have-...his-is-why
EXCERPT: . . . Closely related voles don't show these characteristics, so whatever happened to the creeping vole, it had to have taken place within the past couple of million years.
It's been a puzzle begging to be solved, so biologist Scott Roy and his colleagues decided it was high time to investigate the creeping vole's genes, to work out just what made them so freaky. "This is basically the weirdest sex chromosome system known to science," says Roy.
What they uncovered is even stranger than Ohno would have ever imagined. Starting with the male, Roy and his team used cutting edge genetic sequencing technology to come up with scaffolds representing complete chromosomes.
They also used RNA sequencing to get a sense of what all of the genes were making in both the male and female voles, and compared this with similar transcript libraries taken from females of the related prairie vole (M. ochrogaster).
All of this revealed that there was no Y chromosome, at least in a form we might find in other mammals, such as rats and mice. What Ohno had labelled a Y chromosome turned out to be a fusion of ancestral X and a small handful of Y sequences.
On closer inspection of the female's X chromosome, the team found it was also a chimera of old genes, some of which included ancestral Y genes. These were now only expressed in female creeping voles.
That all adds up to a sex determination system made entirely of two X chromosomes, distinguished only by a small selection of old Y-genes. How females avoid becoming males, especially with the crucial sex-determining region Y (SRY) gene located on their X chromosome, just introduces further mystery.
It's all rather topsy-turvy, not to mention completely unexpected... (MORE - details)
EXCERPT: . . . Closely related voles don't show these characteristics, so whatever happened to the creeping vole, it had to have taken place within the past couple of million years.
It's been a puzzle begging to be solved, so biologist Scott Roy and his colleagues decided it was high time to investigate the creeping vole's genes, to work out just what made them so freaky. "This is basically the weirdest sex chromosome system known to science," says Roy.
What they uncovered is even stranger than Ohno would have ever imagined. Starting with the male, Roy and his team used cutting edge genetic sequencing technology to come up with scaffolds representing complete chromosomes.
They also used RNA sequencing to get a sense of what all of the genes were making in both the male and female voles, and compared this with similar transcript libraries taken from females of the related prairie vole (M. ochrogaster).
All of this revealed that there was no Y chromosome, at least in a form we might find in other mammals, such as rats and mice. What Ohno had labelled a Y chromosome turned out to be a fusion of ancestral X and a small handful of Y sequences.
On closer inspection of the female's X chromosome, the team found it was also a chimera of old genes, some of which included ancestral Y genes. These were now only expressed in female creeping voles.
That all adds up to a sex determination system made entirely of two X chromosomes, distinguished only by a small selection of old Y-genes. How females avoid becoming males, especially with the crucial sex-determining region Y (SRY) gene located on their X chromosome, just introduces further mystery.
It's all rather topsy-turvy, not to mention completely unexpected... (MORE - details)