MK546 has the genotype
age-1(
hx546) 6) II
unc-31(
e169) IV;
age-1 is a mutation conferring extended life and a 70% reduction in brood size. It is tightly linked to
fer-15. By this criterion the
age-1 locus has been mapped to linkage group II. MK546 is male sterile, but reisolates from crosses to N2 are male fertile, albeit at a reduced level. An
age-1 reisolate, TJ401, carries
fer-15 and is Brd (has about 30% of the progeny of N2) as was true for all other long-lived reisolates of
age-1. We have performed a series of three-factor crosses both to precisely localize the position of
age-1 and to separate by recombination the Brd and Age phenotypes, if possible. A three-factor cross using
dpy-10(
e128) 44) II was performed by crossing TJ401 males with the double mutant and cloning Unc non-Dpy and Dpy non-Unc F3 progeny; subsequently, assays for Brd, Age, and Fer were performed on their progeny. Among the recombinants were 8 Fer 10 non-Fer Dpy non- Unc, and 1 recombinant non-Fer Unc non-Dpy. The recombinants were scored for Brd by assaying the number of progeny produced by 3 individuals. Parents were allowed to lay on individual plates and were transferred every 2 days until sterile. The progeny were counted 1 day after the removal of the parents. All Fer recombinants were Brd, and all non-Fer recombinants were non-Brd. This places the
fer-15 and brd loci 0.5 to 1.5 map units to the right of
dpy-10. Scoring of Age proved difficult because
unc-52 significantly reduces life-span. A second three-factor cross using
dpy-10(
e128) 0) II allows more precise mapping. 58 recombinants were analyzed: 25 were Dpy non-Unc and 33 Unc non-Dpy. Brd was scored as before and again showed complete linkage between
fer-15 and brd. The following data position brd and
fer-15 0.6 map units to the right of
dpy-10.[See Figure 1] The
dpy-10 and
unc-4 loci affect life-span. Since
age-1 is recessive with regard to life-span, we have been trying to score life- span on
dpy-10 or
unc-4 F1 heterozygote males obtained by backcrossing recombinants to TJ401. Controls consisted of N2 males, F1 males of
unc-4 by TJ401 males, F1 males of
dpy-10 by TJ401 males, and TJ401 males. Our data currently suggests that the
age-1 gene may be separable from the brd and
fer-15 genes by as much as 0.5 map units, but we remain uncertain of the interpretations of the
age-1 genotype derived from the analysis of heterozygotes. A third three-factor cross is underway using a triple heterozygote (
dpy-10 unc-4) male, test-crossed to
dpy-10 odites. Wild-type recombinants in the male can be identified and subsequently scored for Age and Brd without the interference of the
dpy-10 and
unc-4 mutant loci which make difficult the reliable scoring of the life-span phenotype of the
age-1 locus.