Worm Breeder's Gazette 8(3): 41

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.

A Dominant Suppressor of dpy-26

L. De Long, B. Meyer

We have sought suppressors of dpy-26(n199) as a means of obtaining 
mutations in genes that interact with dpy-26 or that are involved in 
general with regulating the expression of X-linked genes.  dpy-26(n199)
is a maternal-effect, hermaphrodite-specific lethal mutation.  XX 
animals derived from XX animals heterozygous for the dpy mutant allele 
are slightly Dpy; XX animals derived from homozygous animals are 
usually dead (occasionally there are escapers).  dpy-26 mutations also 
result in a recessive Him phenotype producing 5% XO animals; these 
males are essentially wild type.  In order to obtain suppressors of 
n199 we selected for hermaphrodite survivors from animals homozygous 
for n199.  In particular we mutagenized the strain dpy-26(n199) 
)/nT1 (IV:V) n752 with EMS, picked F1 animals 
displaying the unc-22 twitcher phenotype and scored their progeny for 
viable hermaphrodites.  In this procedure s7 is used as a visible 
marker to identify animals homozygous for n199.  nT1 balances the 
right side of chromosome IV.  
The most frequent class of putative suppressors turned out to be 
animals which had acquired a new unc-22 mutation on the nT1 chromosome.
However, one mutant was isolated which acts as a dominant suppressor 
of all the dpy-26-associated phenotypes.  This mutation has the 
following additional properties: 1) It also suppresses the closely-
linked mutation unc-31(e169).  2) A true breeding suppressed strain 
cannot be isolated.  3) When suppressed and nonsuppressed 
hermaphrodites are stained with DAPI and their chromosomes examined a 
very large free duplication appears in the oocytes of the suppressed 
hermaphrodites but is absent from the oocytes of the nonsuppressed 
The duplication (yDp1) is probably a breakdown product of nT1 and 
may contain portions of both chromosomes IV and V.  We are presently 
mapping the chromosomal location and extent of yDp1.