Genetics- mono and dihybrid crosses

[MitsuShai]

There is one part that I can't figure out the answer to on my genetics homework which is finding out what genotype will give 3:1 . I've tried using so ways but I really think getting those ratios is impossible; I honestly don't see any way but I really don't want to right that down. I was at first thinking that 3:1 has to be a mono hybrid cross but now I'm thinking that 3:1 can somehow be a dihybrid cross (if you reduce the numbers or something). I honestly can't get a genotype for this.

 

[epenguin]

Crossing Aa with Aa where a is recessive gives phenotypes in 3:1 ratio and this is elementary, but maybe that is not your question, actually

out what genotype will give 3:1 .

does not seem very clear or meaningful.

 

[MitsuShai]

Crossing Aa with Aa where a is recessive gives phenotypes in 3:1 ratio and this is elementary, but maybe that is not your question, actually



does not seem very clear or meaningful.

yeah I know that, I was asking for how the genotype can be 3:1


I think it has something to do with epistasis.
There was another ratio on my homework that was tough to figure out and it was finding the genotypes that can lead to a 13:3 ratio. I applied epistasis and I got Ww+bb+ x Ww+bb+ as my answer but then I thought about this for a second and I am not thinking that that cross does not give me the genetic ratio but the phenotypic ratio...I don't know anymore, can anybody help?