Worm Breeder's Gazette 2(2): 22b

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.

Lethal Mutations Generated at Different Dosages of EMS

D.L. Baillie, D.G. Moerman, A.M. Rose, K.R.C. Riekki

The effect of E.M.S. dosage on the rate of sex linked lethal 
induction has been investigated at four different concentrations of E.
M.S.; .0125 M, .025 M, .05 M, and .1M.  A control, using no E.M.S. was 
run in parallel.  Mutagenized dpy-5 worms were self crossed and the F1 
subsequently mated to N-2 males so that the F2 sex ratio could be 
scored.  The rate of x-linked lethal induction at .05 M was found to 
be 25%, in close agreement with previous experiments in our lab.  A 
fractionation of broods into three 24 hour egg lays revealed that the 
highest frequency of x-linked lethals occurs at .05 M in brood three.  
Broods one and two appear to have a lower rate of induced lethals, 
which may be explained (at least in brood one) by the fact that the 
mutagenized parent contained fertilized eggs insensitive to E.M.S.  
treatment.  Almost all F1 individuals in brood three (.05 M  E.M.S.) 
carried a sex linked lethal.  The x-linked lethal induction rate is 
seriously affected by the stage of gametogenesis, at the time of E.M.S.
treatment.  Double hit mutations modify the deceptively simple 
relationship between E.M.S. concentration and lethal induction rate, 
lowering it at higher concentrations.  At .05 M  E.M.S. (standard 
dosage), the number of lethal hits is high, and this should be taken 
into consideration when choosing a dosage for the generation of point 
This study has support by a grant from the National Research Council 
of Canada.