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发帖数: 801 | 1 所有的灵长类都有24对染色体，只有人有23对，为什么？
http://en.wikipedia.org/wiki/Chromosome_2_(human)
All members of Hominidae except humans have 24 pairs of chromosomes. Humans
have only 23 pairs of chromosomes. Human chromosome 2 is widely accepted to
be a result of an end-to-end fusion of two ancestral chromosomes.[3][4]
Fusion of ancestral chromosomes left distinctive remnants of telomeres, and
a vestigial centromereThe evidence for this includes:
The correspondence of chromosome 2 to two ape chromosomes. The closest human
relative, the chimpanzee, has near-identical DNA sequences to human
chromosome 2, but they are found in two separate chromosomes. The same is
true of the more distant gorilla and orangutan.[5][6]
The presence of a vestigial centromere. Normally a chromosome has just one
centromere, but in chromosome 2 there are remnants of a second centromere.[7]
The presence of vestigial telomeres. These are normally found only at the
ends of a chromosome, but in chromosome 2 there are additional telomere
sequences in the middle.[8]
Some argue that chromosome 2 presents very strong evidence in favour of the
common descent of humans and other apes. According to researcher J. W. IJdo,
"We conclude that the locus cloned in cosmids c8.1 and c29B is the relic of
an ancient telomere-telomere fusion and marks the point at which two
ancestral ape chromosomes fused to give rise to human chromosome 2." [8] |
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