Worm Breeder's Gazette 11(1): 61

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Pharyngeal Pumping Genetics

Leon Avery

Figure 1

In the May '88 WBG (WBG 10(2): 39), I described a screen for mutants 
whose feeding is abnormal.  The collection, still growing, stands as 

[See Figure 1]
The classification is an attempt to make sense of the diversity of 
phenotypes, and shouldn't be taken too seriously.  There is no pair of 
genes whose mutant phenotypes are not distinguishable.   (Well, 
possibly e2337 and ad462.)  I have classified genes as neuronal or non-
neuronal depending on whether the mutant feeding behavior looks like 
something I could phenocopy by killing pharyngeal neurons.  In some 
cases the distinction is clear.  For instance, the muscle mutants all 
show abnormalities in pharyngeal muscle birefringence, and pha-2 has a 
misshapen pharynx.  unc-26 and unc-36 have been shown by mosaic 
analysis to be necessary in ABp-derived cells for normal locomotion, 
so the classification of these as neuronal is probably also correct.  
The apparent bias of X-ray-induced mutations towards slippery pharynx 
phenotypes is an artefact; I only learned to recognize these recently, 
and haven't done any EMS mutageneses since.  Using the usual 
implausible assumption of equal mutability for all genes, I estimate 
there are about 80 genes (42-201 with 95% confidence) that mutate to 
produce non-lethal feeding abnormalities, about 50 neuronal and 30 non-
neuronal.  Of these 80, about 30 would be in genes already known 
because of effects on other behaviors, and 50 would be previously 
unknown, at least as behavioral genes; some could be essential.

Figure 1