Mhc class II genes of Darwin’s Finches: divergence by point mutations and reciprocal recombination

摘要: The 15 species of Darwin’s Finches are one the classical examples adaptive radiation — divergence a single ancestral into multiple forms adapted to various ecological niches. As such they provide an opportunity study evolution major histocompatibility complex (Mhc) genes in period radiation. In present two families Ground Finch Geospiza scandens from Daphne Major Island Galapagos Archipelago were sampled and exon 2 their Mhc class II B was sequenced. sequences indicate that unlike domestic fowl with its compact, gene-poor Mhc, contains more than half dozen loci alone. Roth intron suggest at different closely related some them may have diverged another during on Archipelago. seem arisen by multiplication hexamer TCCCAG, ultimately reaching length ~ kb. repeats still clearly recognizable introns loci. Sequence motifs specify polymorphic residues putative peptide-binding region (PBR) β2 domain. can be explained sequential accumulation point mutations incorporation (or fixation) balancing selection. individual is best this process combined occasional reciprocal recombination shuffled motifs.