Survivals of C. elegans wild-type strain CL2a, the lsq4- congenic line SR701, and seven recombinants derived from SR701 during two final generations of backcross to CL2a. These recombinants were detected by loss of the Bergerac-BO allele at one or two of the lsq4 markers (stP13, stP44, stP35), and homozygotes of each were ascertained, expanded, and used to measure survival in liquid medium at 20°C. (A,B) are independent survival experiments conducted sequentially. Procedures for nematode culture, scoring, and survival analysis are described in the “Materials and Methods” section. Numbers of worms initiated and scored per survival, median, and maximal life-spans, and significance of differences among the groups, are summarized in Table 1. Adult age is measured in days following the L4 larval stage; total age is therefore the indicated adult age plus 2.5 days. (C) Diagram of lsq4 mapping data. Markers in the stP13–stP35 region are indicated by vertical bars. Horizontal two-headed arrows represent genetic-map spans of the introgressed (Bergerac-BO allele) regions, for congenic line SR701 and seven recombinants thereof. Long-lived recombinant lines (life-spans similar to CL2a) are named at the left, while those named on the right were shorter-lived. The 26 new markers obtained by Anchor-PCR Display, and three previously determined markers in this vicinity (Williams et al., 1992), were ordered into 10 groups by the seven recombinant lines; eight of these are indicated by cross-striped vertical bars. Based on these data, the longevity QTL lies between marker groups G7 and T6 (shaded rectangle, 13.15–14.33 Mb). Several of the SNPs in this region that distinguish between parental strains are indicated by triangles at the figure bottom; symbols are green/open if SR708 carries the CL2a allele; and red/filled if SR708 carries the Bergerac-BO allele. SNPs shown here, named for YAC clones in which they reside, are: snp_Y67H2A (13.27 Mb), snp_W02A2/pkP4053 (13.35 Mb), snp_Y45F10A/pkP4059 (13.49 Mb), snp_Y45F10B (13.55 Mb), snp_Y45F10C (13.65 Mb), snp_Y37A1A (13.83), and snp_C27H2 (13.95). SNPs with “pkP” are snip-SNPs.