Worm Breeder's Gazette 9(2): 80

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.

Saturation Screen for Lethals on Linkage Group V (left)

R.C. Johnsen and D.L. Baillie

We are attempting to saturate and map essential genes and steriles 
on the left half of linkage group V.  This region ( 20 map units and 
7% of the entire genome) is balanced by the crossover suppressor eT1(
III;V) which also balances the right arm of LG III.
From an initial screen of 2738 'chromosomes', treated with 0.012M 
EMS, we have isolated 147 eT1 balanced recessive lethal and sterile 
mutations.  Thirty-five percent of these lie on LG V (left) and sixty-
five percent are on LG III (right).
A Poisson calculation predicts that a screen of 15, 000 chromosomes 
should yield a mutation in ninety-five percent of the genes.  We are 
in the process of screening another 10,900 'chromosomes' from which we 
have isolated 755 lethal and sterile mutations: 255 ( 36.8% ) of these 
are on LG V, 438 are on LG III lethal (and have been discarded) and 
the mutations of 62 strains have not yet been mapped.
We are also screening 3000  0.07% formaldehyde treated 'chromosomes'.
This should yield two results: 1) the mutation rate for 0.07% 
formaldehyde over a well characterized region, eT1 (III,V) and 2) a 
set of 20-30 short (1-2 m.u.) deficiencies on LG V (left).
Breakpoints from these deficiences will divide LG V (left) into more 
zones than the fourteen that have already been established (see 
Rosenbluth et al.  this issue).  The mapping of the 200 plus lethals 
to specific zones and against known genes in those zones, will then 
give the distribution of essential genes along the chromosome.  The 
mapping already done shows that they follow a non-uniform distribution.

This research has been supported by NSERC and Muscular Dystrophy 
Association (Canada) grants to DLB.