Punnet Square - Monohybrid Out-Cross

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Punnet Square - Monohybrid Out-Cross

Post by Roxlo » Sun Nov 01, 2009 3:00 am

Ok so I know this should probably be easy but I haven't done genetics in a while. Can anyone give me some insight/how to set this up?

It is a monohybrid out-cross, and it says to complete the punnet square for the parental cross.

Female: dpy-5(e61) / dpy-5(e61)
Male: dpy-5(e61) / dpy-5(+)

I've gotten the genotypic ratio of the F1s (2 dpy-5(e61) : 2 dpy-5(+)), and phenotypic ratio of 1:1 (assuming dpy-5(e61) allele is recessive to the wild type (+) allele, but the next part of the question asks:

If dpy-5(e61) allele is semi-dominant to the wild type (+) allele, what would you predict for the phenotypic ratio for the cross?

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Post by JackBean » Fri Dec 25, 2009 8:25 pm

let's say, e61 will be E and + will be P(lus), OK?
so, female is EE and male is EP. So, offspring will be EE : EP in 1 : 1, so if E is actually recessive, than the phenotype will be E : P in 1 : 1 (half are homozygotes and half are heterozygotes and these look like dominant homozygotes;)

If E would be semi-dominant, the phenotypic ratio should be the same, because each, recessive homozygot, heterozygote and dominant homozygote should look different, but you have only two genotypes anyway ;)

Cis or trans? That's what matters.

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