Thursday, March 17, 2005
EVOLUTION IN ACTION:
I borrow Pournelle's phrase for this story, spotted by Sheila Lennon of Subterranean Homepage News:
I borrow Pournelle's phrase for this story, spotted by Sheila Lennon of Subterranean Homepage News:
With more than 1,000 genes and 160 million base pairs of DNA, the X looms like a giant next to the stunted Y chromosome that produces males. The Y chromosome -- 78 genes, 23 million DNA subunits --was sequenced in 2003. ...
Until mammals began to replace reptiles and rule the Earth about 300 million years ago, the X and Y were of equal size and able to swap genetic material.
But over eons, the male-producing Y has been riddled by mutations, and the trading of genes trailed off. The chromosome withered away in size, and its function became limited to establishing maleness, ordering the building of male sexual organs and conferring the ability to produce sperm.
The X acquired more responsibilities and genes while the Y "slowly but surely dropped off the face of the Earth ... Although it contains a few important genes, it's almost like the appendix of the human genome."
