Worm Breeder's Gazette 9(2): 100

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Analysis of the age-1 Locus by Three-Factor Crosses

P. Fitzpatrick and T. Johnson

Figure 1

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 
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.

Figure 1