skn-1 strain / worm genetics help

Model Organism: Worms Methods & Reagents
1

Hello Worm Community,

I’m no expert in worm genetics, but I try my best.
I have a question for you, which may be easy for you to answer.

I bought this strain from the CGC:
Strain: EU1
Species: Caenorhabditis elegans
Genotype: skn-1(zu67) IV/nT1unc-?(n754) let-?.
Description: Heterozygotes are Unc and segregate Unc, WT which give only dead eggs, and dead eggs. Maintain by picking Unc.
Mutagen: EMS
Outcrossed: x8

I wanted to understand the genetics of this strain so I read a bit about balancers and skn-1.
This is what I think is going on. Can you confirm/reject this?

A skn-1 heterozygote has a genotype of + + skn-1 / unc let +
When it selfs, it makes the following three (and because of the balancer we assume no recombination):

    • skn-1 / + + skn-1 (WT which give only dead eggs–a skn-1 homozygous defect)
    • skn-1 / unc let + (unc, heterzygotes of skn-1)
      unc let + / unc let + (dead eggs, because of the homozygosity of let)

Again, can you confirm whether this sounds about right?

Also, I read that skn-1 homozygotes lack a pharynx. How do they eat then?
I thought skn-1 homozygotes would have trouble eating and therefore slower development but I did not see any delay in their development.

THANKS!

2

I don’t know much about skn-1, and can’t speak to your question about a pharynx defect, or growth rate.

Your progeny classes are mostly correct, except that you’re missing the aneuploids: because the nT1 balancer is a reciprocal translocation, 10/16 of the zygotes from selfing the translocation-heterozygote will be aneuploid, which is lethal. For more on this see Rosenbluth and Baillie, or work out the Punnett squares. You should get 10 aneuploids : 4 translocation-heterozygotes : 1 translocation-homozygote : 1 non-translocation-homozygote.

Also, if you’re planning to use this strain extensively, you may find it convenient to use a version of nT1 marked with the gfp trangene qIs51 rather than the Unc marker n754.