Worm Breeder's Gazette 10(1): 99

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A Little Uncoordinated Genetics

D. Thierry-Mieg

Figure 1

To get familiar with C.  elegans, I did some genetics, and generated 
in particular a map of the centre of the X.
[See Figure 1]
Note the new position of vab-3, and the allelism of unc-27 and unc-
99.  Genes seem to cluster in the dpy-7 to vab-3 interval.
The only previously known allele of unc-110, e1913, is a dominant 
Unc resembling unc-93 and a recessive larval lethal.  A dosage series 
of unc-110, using nDf-19, stDp-2 or triplo-X was constructed.  
Interestingly, the phenotypes of the hermaphrodites could be ordered 

[See Figure 
e1913 is therefore an antimorphic allele whose phenotype is an 
accurate representation of the dosage.  It is also dosage compensated 
: unc/+;tra-1 males have an Unc phenotype similar to unc/+ 
hermaphrodites and do mate, whereas unc/0;stDp-2(X,IIC)[unc-110+] are 
extreme Uncs and are sterile.  Incidently, this would make unc-110 (
e1913) a good tool for selecting mutants that modify dosage 
compensation in either direction.  In a search for amorphic alleles of 
unc-110, 5 independent revertants (in 501 progeny from 74) were 
collected after EMS treatment.  Four were inseparable from e1913 and 
are probably amorphs.  They are homozygous viable and nearly wild type;
that the unc-110 gene product appears to be redundant.
Primarily interested in the building of the nervous system, I also 
mapped nine pseudo-spontaneous unc alleles isolated by R.  Hoskins, J. 
Mancillas, L.  Nawrocki and me.  To my surprise, four of them defined 
new unc loci 
unc-115 : strong kinker, amorph, XC, between unc-58 and vab-3,unc-
116 : L1 coiler, hypomorph, IIIC, 0.06u to the right of unc-86, in the 
unc-86 contig.
unc-117 : larval kinker, XL, <0.2u from unc-20.unc-118 : kinker, XC, 
between unc-90 and unc-58.  The amorph, if viable, is probably sterile.

High number uncs should not be despised.  unc-116 (e-2310), isolated 
by J.  Mancillas, has a number of cell nuclei mispositioned in the L1. 
The hyp7 contralateral nuclear migration is impaired in the very same 
manner as in unc-83 and unc-84, and the hyp7 nuclei lie in the dorsal 
hypodermal ridge.  Electron microscopy also shows some variable 
mispositioning of a number of lateral axons.  In one animal out of 
three, one ALM runs in the dorsal cord, as noticed by Nichol Thomson.

Figure 1