Women's Chromosome Division Different From Men's
A HUMAN OOCYTEA human oocyte in meiosis. Protein complexes that bind homologous (partner) chromosomes are shown in red, proteins that mark sites of cross-overs are in yellow, and proteins associated with centromeric regions are in blue. Other "splashes" of color come from DNA probes that recognize specific human chromosomes.Hassold, et al.
PHILADELPHIA — Women and men sometimes do things differently, right down to divvying up their genetic legacies.
This divvying up is known as meiosis, a process that cuts the number of chromosomes in half during the production of eggs and sperm. Men do meiosis by the textbook, but women play it looser with the process, scientists from Washington State University and the University of Washington reported Nov. 12 in Philadelphia at the annual meeting of the American Society of Human Genetics.
The finding could help explain why women sometimes pass along the wrong number of chromosomes to their children, the researchers suggest. “The male doesn’t contribute to chromosome abnormality in any way,” says Terry Hassold, a geneticist at Washington State University in Pullman who presented the findings.
Some genetic disorders, such as Down syndrome, are caused by having an extra copy of a chromosome. Humans normally have two copies of each chromosome, one inherited from mom and one from dad. About one in every 700 babies born has an extra copy of chromosome 21, a surplus that causes Down syndrome. About one in every 1,000 babies born may have an extra X or Y chromosome, and one in every 1,000 girls may have only one X chromosome. Abnormalities in the number of other chromosomes often lead to miscarriage or to death soon after birth.
Humans are the only species known to have a high rate of error in the number of chromosomes they pass along, Hassold says. About 25 percent of all fertilized human eggs have the wrong number of chromosomes, he says.
“It’s a major problem and it’s only getting worse” as more older women have children, he...
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