The human genome harbours widespread exclusive yin yang haplotypes

There have been reports of examples of exclusive yin yang haplotypes, differing at every locus, but there has been no systematic search for them. Unphased whole genome sequence data for 2504 unrelated 1000 Genomes subjects was searched for chains of SNPs having global minor allele frequency (MAF) > =0.1 made up of at least 20 SNPs in complete linkage disequilibrium with each other and with no pair being separated by more than 9 other SNPs. The global distribution of these haplotypes was investigated, along with their ancestral origins and associations with genes and phenotypes. A number of previously unrecognised repeats were noted, flagged by all or most subjects being called as heterozygotes, and these were discarded. There were 5114 exclusive yin yang haplotypes each consisting of on average 34.8 SNPs, each spanning on average 15.7 kb and cumulatively covering 80 Mb. Although for some haplotypes the MAF varied markedly between populations the average global fixation index was similar to that for SNPs elsewhere in the genome and there was no evidence of enrichment for genes or gene ontologies. For all but 92 haplotypes there were partial forms present in the chimpanzee and/or Neanderthal genome, indicating that they had been formed in a gradual process but that intermediate haplotypes were now absent from modern humans. Exclusive yin yang haplotypes cover over 2% of the human genome. The mechanisms accounting for their formation and preservation are unclear. They may serve as useful markers of the dispersal of chromosomal regions through human history.