With Men’s Y Chromosome, Size Really May Not Matter
by Rob Stein/NPR
Basic biology has it that girls are girls because they have two X chromosomes — the things inside cells that carry our genes. Boys are boys because they have one X and one Y. Recently, though, there’s been a lot of debate in scientific circles about the fate of that Y chromosome — the genetic basis of maleness.
Click to see SEMs of Human Chromosomes
Very early in the evolution of the Y chromosome, explains Dr. David Page, a geneticist at the Massachusetts Institute of Technology, something pretty dramatic happened: The ancestral Y lost most of its genes. And scientists basically ignored the little that was left.
"The Y chromosome was essentially written off as the runt of the human genome," Page says, "as a sort of genetic wasteland that didn’t really merit anyone’s serious attention."
When the Y did get any attention, it wasn’ t good news. Some scientists, like geneticist Jennifer Graves at La Trobe University in Melbourne, Australia, speculated that the Y might be destined to just keep, sort of … rotting away.
"As soon as it becomes a male-determining chromosome, then the rot sets in," La Trobe says. "That’s kind of the kiss of death for that chromosome" — meaning the Y chromosome could be headed toward oblivion, completely disappear.
But other scientists, including Page say: Not so fast. Step away from my Y chromosome.
"I’ve really spent the better part of my career defending the honor of the Y chromosome in the face of insults of this sort," Page says.
For the Y, size really doesn’t matter, he says. Page has done a detailed analysis of the chromosome’s evolution and says the string of genes has been solidly stable now for millions of years.
"The idea that the Y chromosome might disappear altogether, possibly taking men with it — I think that idea has now been firmly dismissed," he says.
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