January_28_2013_NKW_NEW

One reason a new mutaon is inially in linkage

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Unformatted text preview: at paired sites Haplotype Blocks: 8000 base pairs of a human chromosome B1 Linkage Equilibrium is approached but NOT in 1 genera+on (contrast to Hardy ­Weinberg Equilibrium) rate depends on linkage between the loci. 8000 base pairs of a human chromosome DIPLOID GENOTYPES A1 B1 GENOTYPE FREQ GAMETE FREQ Based on genotyping 37 Bri+sh individuals (54 haplotypes) AJ Jeffreys et al. 2003. 5 Haplotype Blocks occur between recombina+on hotspots: genotype of one male (dots= SNPs) How does Linkage Disequilibrium arise in a popula+on? ONE REASON: A new muta+on is ini+ally in Linkage Disequilibrium because it occurs on a par+cular haplotype background. All 4 possible Star+ng 2 muta+on 3 recombina+on Haplotypes Haplotypes B  B Haplotypes 1 2 A1 B1 A1 B1 A1 B1  haplotypes of recombinant sperm % of recombinant sites B1 A2 B2 A2 A2 B1  A1 B2 A2 A2 B2 B1 KEY FOR US IN THIS CLASS: But the 4th haplotype (A1 B2) may not appear for a long :me if the two loci are closely linked on the chromosome (within a Haplotype Block) Therefore closely linked regions of the chromosome will tend to share SNP...
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