Gene conversion and natural selection in the evolution of X-linked color vision genes in higher primates.
During higher primate evolution, gene conversion seems to have occurred often between the red and green photo-pigment genes, which are tandemly linked on the X chromosome. To understand this phenomenon better, intron 4 sequences of the red and green pigment genes of a male human (an Asian Indian), a male chimpanzee, and a male baboon were amplified by PCR and sequenced. The data show that the intron 4 sequences between the two genes have been strongly or completely homogenized in the three species studied. Apparently recent gene conversion events have occurred in introns 4 of the red and green pigment genes in humans and chimpanzees. Two or more conversion events may have occurred at different times in introns 4 of the two pigment genes in baboons. The divergence between the two genes is significantly lower in intron 4 than in exons 4 and 5 in each species, contrary to the usual situation that introns evolve faster than exons. It is most likely that strong natural selection for maintaining the distinct functions of exons 4 and 5 of the red and green pigment genes has acted against sequence homogenization of these exons.
Zhou
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YH
Human Genetics Center, University of Texas Health Science Center, Houston 77225, USA. li@hgc.sph.uth.tmc.edu
Li
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WH
D000818:Animals; D044466:Asian People / Q000235:genetics; D001483:Base Sequence; D003118:Color Perception / Q000235:genetics*; D019143:Evolution, Molecular; D005091:Exons / Q000235:genetics; D005785:Gene Conversion; D006801:Humans; D007438:Introns / Q000235:genetics; D008297:Male; D008969:Molecular Sequence Data; D002679:Pan troglodytes / Q000235:genetics; D010215:Papio / Q000235:genetics; D011323:Primates / Q000235:genetics*; D017299:Rod Opsins / Q000235:genetics*; D012641:Selection, Genetic; D013045:Species Specificity; D044465:White People / Q000235:genetics; D014960:X Chromosome / Q000235:genetics*
D017299:Rod Opsins; C095855:long-wavelength opsin; C095854:middle-wavelength opsin