MBIO 3430 Lecture Notes - Lecture 19: Chemokine Receptor, Ccl3, Gene Duplication
23 Nov 2018
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Different conditions favour the increase for the same allele (at different times) A shift in the function of a trait during evolution. Ccr5 gene: chemokine receptor type 5 (co-receptor for hiv) The ccr5 32 allele -> 32 base pair deletion. Found in caucasian populations from central europe. Ccr5 32 if homozygous immunity to aids. If heterozygous a delay in the progression of aids. Proposal: 32 provides resistance to bubonic plague (yersinia pestis) There is no actual evidence that this mutation provides immunity to the plague: lack of human volunteers, also mouse model failed to provide any evidence. Could also have come from obstructing the pathway for smallpox infection. Diploid cells have 2 copies but can have more copies (due to intrachromosomal duplication: up to 6 (or more) can provide some immunity to hiv. Phenotypes due to one or many alleles. A balancing act within a population frequencies of various alleles determine the range of diversity for each phenotype.
