Between humans and chimpanzees, as is well known, there is a difference of just ~1.24% of their DNA sequences, but studies have confirmed that a substantial number of chromosomal rearrangements have occurred, nine chromosomes exhibit pericentric inversions between these species, and human chromosome 2 shows a fusion of two acrocentric chromosomes present in chimpanzees (chromosomes 12 and 13) and other great apes (chromosomes 11 and 12 in gorillas and orangutans)!. Furthermore, some authors has been proposed that protein evolution would happened more than 2.2 times faster in chromosomes that had undergone structural rearrangements compared with colinear chromosomes. Recent studies have suggested that gene gain and loss in the Y-chromosomes may contribute significantly to the divergence between humans and chimpanzees. Initial comparisons of the human and chimpanzee Y-chromosomes indicate that chimpanzees have a disproportionate loss of Y-chromosome genes, which may have implications for sex-specific as well as reproductive traits.
Chromosome rearrangements like inversions, fussions or fissions are strong genetic reproductive barriers because they reduce recombination between heterokaryotypes and facilitate divergence, Thus “monstrosities” such as a chromosome change are key processes in the diversification of parapatric or sympatric populations. In spite of the relevance of cytogenetic processes, until today's day the degree of chromosomal differentiation necessary to consider two organisms as belonging to different species is unknown... Too much of faith in allmigthy structural DNA sequence Maybe?...
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