![]() DNA sequence and comparative analysis of chimpanzee chromosome 22. Initial sequence of the chimpanzee genome and comparison with the human genome. ![]() The Chimpanzee Sequencing and Analysis Consortium. ![]() Occurrence of a transposition from the X-chromosome long arm to the Y-chromosome short arm during human evolution. The male-specific region of the human Y chromosome is a mosaic of discrete sequence classes. The AZFc region of the Y chromosome features massive palindromes and uniform recurrent deletions in infertile men. Has the chimpanzee Y chromosome been sequenced? Nature Genet. Comparative analysis of chimpanzee and human Y chromosomes unveils complex evolutionary pathway. Conservation of Y-linked genes during human evolution revealed by comparative sequencing in chimpanzee. The master sex-determination locus in threespine sticklebacks is on a nascent Y chromosome. A primitive Y chromosome in papaya marks incipient sex chromosome evolution. Reduced adaptation of a non-recombining neo-Y chromosome. Low variability in a Y-linked plant gene and its implications for Y-chromosome evolution. The temporal dynamics of processes underlying Y chromosome degeneration. Four evolutionary strata on the human X chromosome. Evolution of the Y sex chromosome in animals. Although genetic decay may be the principal dynamic in the evolution of newly emergent Y chromosomes, wholesale renovation is the paramount theme in the continuing evolution of chimpanzee, human and perhaps other older MSYs. We suggest that the extraordinary divergence of the chimpanzee and human MSYs was driven by four synergistic factors: the prominent role of the MSY in sperm production, ‘genetic hitchhiking’ effects in the absence of meiotic crossing over, frequent ectopic recombination within the MSY, and species differences in mating behaviour. The chimpanzee MSY contains twice as many massive palindromes as the human MSY, yet it has lost large fractions of the MSY protein-coding genes and gene families present in the last common ancestor. By comparing the MSYs of the two species we show that they differ radically in sequence structure and gene content, indicating rapid evolution during the past 6 million years. Here we finished sequencing of the male-specific region of the Y chromosome (MSY) in our closest living relative, the chimpanzee, achieving levels of accuracy and completion previously reached for the human MSY. These theories have been buttressed by partial sequence data from newly emergent plant and animal Y chromosomes 5, 6, 7, 8, but they have not been tested in older, highly evolved Y chromosomes such as that of humans. Prevailing theories hold that Y chromosomes evolve by gene loss, the pace of which slows over time, eventually leading to a paucity of genes, and stasis 3, 4. Little is known about the recent evolution of the Y chromosome because only the human Y chromosome has been fully sequenced. The human Y chromosome began to evolve from an autosome hundreds of millions of years ago, acquiring a sex-determining function and undergoing a series of inversions that suppressed crossing over with the X chromosome 1, 2.
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