The set of LXS recombinant inbred (RI) strains is a new and exceptionally large mapping panel that is suitable for the analysis of complex traits with comparatively high power. This panel consists of 77 strains - more than twice the size of other RI sets - and will typically provide sufficient statistical power (β = 0.8) to map quantitative trait loci (QTLs) that account for ∼25% of genetic variance with a genomewide p < 0.05. To charactrizethe genetic architecture of this new set of RI strains, we genotyped 330 MIT microsatellite markers distributed on all autosomes and the X Chromosome and assembled error-checked meiotic recombination maps that have an average F 2-adjusted marker spacing of ∼4 cM. The LXS panel has a genetic structure consistent with random segregation and subsequent fixation of alleles, the expected 3-4 x map expansion, a low level of nonsyntenic association among loci, and complete independence among all 77 strains. Although the parental inbred strains-Inbred Long-Sleep (ILS) and Inbred Short-Sleep (ISS) - were derived originally by selection from an 8-way heterogeneous stock selected for differential sensitivity to sedative effects of ethanol, the LXS panel is also segregating for many other traits. Thus, the LXS panel provides a powerful new resource for mapping complex traits across many systems and disciplines and should prove to be of great utility in modeling the genetics of complex diseases in human populations.
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