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XYY syndrome and fate of chromosomes in meiosis I

Genetics as it applies to evolution, molecular biology, and medical aspects.

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XYY syndrome and fate of chromosomes in meiosis I

Postby Smachine » Mon Aug 03, 2009 6:08 pm

Hello! First post here. :)

Lately I have been thinking about those syndroms like XXX or XYY, and Im not sure what happends when cells with this kinda karyotype undergo meiosis. From what I have read, a person with this kinda karyotype could produce normal offsprings so what exactly happens with the extra sex chromosome during devision? What kind of gametes does and individual with XYY syndrome form and why?
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Postby MrMistery » Wed Aug 05, 2009 1:24 am

It can produce two types of gametes, depending on what happens in meiosis I: first the extra Y chromosome can go with the other Y, and produce 2 X gametes (which are normal) and 2 YY gametes (which are abnormal, but viable). Then the extra Y chromosome can go with the X, and produce 2 XY gametes (these are viable, and can form zygotes) and 2 Y zygotes (which are normal). then, when the mom contributes her X you'll have:
X + X -> XX normal girl
YY + X -> XYY phenotypically normal guy
XY + X -> XXY Klinefelter syndrome
Y + X -> normal guy.

This reminds me of my high school years doing classical genetics problems like this...
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
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