Intro Genetics

[Pereira]

Hello,

 

I am a little confused about complete dominance. The question I am trying to solve is: A trihybrid pea plant having the genotype AaBbC(1)C(2) is self fertilized there is complete dominance at the A and B loci and co-dominance at the the C loci. What fraction of the progeny will be phenotypically different from the parents?(assume independant assortment).

 

Now I know that the co-dominance C(1)C(2) will show through all the progeny and that A\- & B\- will also be phenotypically alike to the parents. So A\-B\-C(1)C(2) will be phenotypically the same. My question is if A\-bbC(1)C(2), aaB\-C(1)C(2) will cause the progeny to be phenotypically different. As well (correct me if I am wrong) the aabbC(1)C(2) if the homozygous will still be phenotypically different. I know this should be fairly easy but my text is really confusing me at the moment.

 

So far I think that the ratio of differing progeny is 3/4. If I am wrong any help will be appreciated.

 

Thank you.