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Y: not small, not identical, not decaying.
Oct. 8th, 2005 12:37 pmI did a little half-hearted Googling to get at the heart of this X/Y business.
The first hit, at Nature.com, has a little slideshow at the stop that includes Michelangelo's David and Homer Simpson. Amusing.
But the first article on that page indicates that the Y is 23 Mb -- hardly an .INI file, but I have no basis for comparison. I'm satisfied that it's big enough. Even if it weren't, you know, size isn't everything.
My previous mental model was that Y chromosomes never see other Y chromosomes, so they never change except through rare mutations. And the oft-heard assertion that the Y is "decaying" seems like a logical outcome, since it can't recombine the way pairs of X's can. But Y-chromosomes have several long palindrome sequences, which provide both a backup copy of working genes, and a means for keeping the genes dynamic. The same article describes an experiment where they compared Y chromosomes from all over the world, paying special attention to those palindromes. They concluded that "as many as 600 base pairs (from the 5.4 Mb contained in MSY palindromes) must be converted in each newborn male in the human population." If I'm reading this right, this means that the Y-chromosome has a big pile of alternative genes stowed away to keep itself adaptive to change. And also, I don't have the exact same Y as my father.
There's another article that compares this chromosome betweeen humans and apes. But I confess that my science fu is too weak to derive accurate conclusions from this article. It does show that oversimplified statistics about how many genes we share with great apes are of little use, apart from providing evidence that evolution did, in fact, happen. That may be why I was unable to correlate these findings with similar studies done under principles of intelligent design. Sorry.
The first hit, at Nature.com, has a little slideshow at the stop that includes Michelangelo's David and Homer Simpson. Amusing.
But the first article on that page indicates that the Y is 23 Mb -- hardly an .INI file, but I have no basis for comparison. I'm satisfied that it's big enough. Even if it weren't, you know, size isn't everything.
My previous mental model was that Y chromosomes never see other Y chromosomes, so they never change except through rare mutations. And the oft-heard assertion that the Y is "decaying" seems like a logical outcome, since it can't recombine the way pairs of X's can. But Y-chromosomes have several long palindrome sequences, which provide both a backup copy of working genes, and a means for keeping the genes dynamic. The same article describes an experiment where they compared Y chromosomes from all over the world, paying special attention to those palindromes. They concluded that "as many as 600 base pairs (from the 5.4 Mb contained in MSY palindromes) must be converted in each newborn male in the human population." If I'm reading this right, this means that the Y-chromosome has a big pile of alternative genes stowed away to keep itself adaptive to change. And also, I don't have the exact same Y as my father.
There's another article that compares this chromosome betweeen humans and apes. But I confess that my science fu is too weak to derive accurate conclusions from this article. It does show that oversimplified statistics about how many genes we share with great apes are of little use, apart from providing evidence that evolution did, in fact, happen. That may be why I was unable to correlate these findings with similar studies done under principles of intelligent design. Sorry.
