Recombination and LD in C. elegans
Highlights of the paper - by Rockman and Kruglyak (PLoS Genetics 2009, DOI 10.1371/journal.pgen.1000419) - on the patterns of recombination in C. elegans laboratory and wild strains.
A total of 1454 nuclear SNP markers in 236 RIAILs (Recombinant inbred advanced inercross lines) were used. The lines were derived from a 20-generation reciprocal crosses between N2 (Bristol) and CB4856 (Hawaii) strains. The RIAIL genetic map length was found to be 1588 cM (5.3 fold expansion of F2 map).
Five distinct domain were observed on each of the six chromosomes: two tips with effectively zero recombination, two high recombination arms, and a low recombination center. The center domain of each autosome occupies roughly half of the chromosome's length (I: 47.7%, II: 46.7%, III: 48%, IV: 51.9%, V: 50.9%).The X-chromosome center is comparatively much shorter (35.8%).
All centers have roughly similar rates of recombination. Shorter chromosomes have a larger fraction of their recombination events in their arms.
Based on 1460 SNPs that were genotyped from 125 wild isolates only 41 represent distinct haplotypes, suggesting that others may have been derived from early laboratory crosses with the N2 strain.
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The frequency of the N2 allele at each marker along the chromosomes. The expected frequency, 0.5, is represented by the gray line. (from Figure 3 in the paper)
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