LADIES FIRST?

I had this theory that the Y chromosome was actually an congenital defect but never did I think the Y chromosome became that way through evolution. After some external prompts I did a bit of investigation and  Sure enough, according to published reports It was FIRST X then Y ..."ain't" that something?
DISCLAIMER: THE FOLLOWING IS COLLECTED FROM THREE DIFFERENT WEB SITES - I DID NOT DO THE RESEARCH - I ONLY COPIED IT!
The Origin of the Sex Chromosomes.
http://www.abc.net.au/science/news/stories/s63100.htm

Research published in this week's Science reveals that the Y chromosome developed from an X-like ancestor around 300 million years ago.

Researchers at the Howard Hughes Medical Institute have found that the X and Y chromosomes evolved from a standard identical pair around 300 million years ago - shortly after the divergence of the evolutionary lines leading to mammals and birds.

"By fossil digging on the sex chromosomes, we were able to reconstruct the four events that drove sex chromosomes into their distinctive X and Y forms, and to date when these events occurred during evolution," says Lahn. "The farther back in time we look, the more similar X and Y appear, boosting the theory that they arose from a pair of identical autosomes."

Today the X is still home to thousands of genes, but the Y has only a measly few dozen. Nevertheless, many genes on the human Y chromosome have homologues (analogous genes) on the X chromosome. The presence of these X-Y genes reinforces the idea that the Y chromosome developed from an X-like ancestor.
But wait! Poor Y can't exist on its own
http://findarticles.com/p/articles/mi_m1511/is_n2_v16/ai_16051165

...human embryos with a single sex chromosome will continue to develop if--and only if--that chromosome is an X. If a fertilized egg is somehow stuck with a Y chromosome and no X, it's out of luck. The embryo self-destructs very early in development. Put plainly, the Y just doesn't have the resources that human development, male or female, requires. The X chromosome does. Embryos bearing a single X chromosome can develop into healthy (albeit infertile) adults.
BATTLE OF THE SEXES IS REAL?


X vs. Y: The Y-chromosome already looks tiny and weak
compared to the X-chromosome.

http://www.exitmundi.nl/giggle.htm

"On Y, you'll also find stuff that is harmful to women. For example: sperm contains chemicals that attack the woman's body. Really! Semen comes with chemicals that shut down the woman's immune system, so that it can make it into the womb alive.

That's why X, the female chromosome, hates Y. In response, X is constantly throwing all kinds of wicked chemicals at Y. X is killing Y.

Take a look through the microscope, and you can immediately see Y is in trouble. Y is a tiny, crumpled chromosome -- not exactly a proud symbol of manliness. Ever since Y split off from the other chromosomes, some 300 million years ago, its number of genes went down from about 1,000 to 80. How did it ever get so tiny? You guessed it: that's because of the female chromosome's attacks.

Perhaps the most spine-chilling clue comes from the men. As we speak, 1 to 2 percent of all men is infertile because of a malfunctioning Y-chromosome! That doesn't seem like much, but it is an astonishing number, because the defects cannot have been inherited (because they lead to infertility). So in other words: 1 to 2 percent of all men have their Y-chromosome disabled during their life! 


Check out the links. It's great insight on sex chromosomes.

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Posted by Mel at 10/4/2007 12:55 PM
Categories: uncategorized
 

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