Interval mapping of QTL for lifespan and for the regulation of LSK cells. Likelihood ratio statistic (LRS) values (y-axis) along chromosomes 2, 4, and 7 for lifespan and for traits related to the regulation of LSK cells in BXD RI mice, mentioned on top of each panel. The dashed horizontal lines in each panel represent the lower boundaries of LRS values indicating suggestive (lower line) and significant (upper line) genome-wide significance levels as determined by permutation analysis.^25,26  The 2 different panels for lifespan along chr 4 were obtained by correcting for a different primary QT locus: chr 7 in the upper right, and chr 2 in the lower right panel.