Humans have a characteristic diploid chromosome number of 2N=46 whereas the other Great Apes (orangutans, gorillas, and chimps) are all 2N=48. The large metacentric Chromosome 2 of Homo appears to be the result of a fusion between two smaller telocentric chromosomes found in the other Great Apes. In the figure above, Q-banding patterns in the chimp acrocentrics are homologous to those of the 2p (short) and 2q (long) arms of human Chromosome 2: the alignments are indicated. As well, ape telomeres (the ends of chromosomes) characteristically consist of tandem repeats of the motif 5′-TTAGGG-3′. Such sequences are also present In the human centromere (the middle of the chromosome), but at one point the order changes abruptly to 5′-CCCTAA-3′, the reverse complement of the standard pattern, as predicted by a telomere to telomere fusion of ancestral ape-like chromosomes.
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