Extensive polymorphism and different evolutionary patterns of intron 2 were identified in the HLA-DQB1 gene

Exon 2 and intron 2 of the HLA DQB1 gene from 20 individuals were cloned and sequenced and eight alleles were obtained. Based on our analysis, the nucleotide diversity of the 5' end of intron 2 was higher than the synonymous nucleotide diversity of exon 2, which may be due to the lower GC content and the 'hitch-hiking effect'. In contrast, the opposite phenomenon was observed for the 3' end of intron 2, which may be the result of the recombination between the 3' end and 5' end of intron 2 and the subsequent genetic drift. The results indicated that different regions of intron 2 in the DQB1 gene had different evolutionary patterns.