Another Monohybrid Inheritance Problem...?

Question

If a spotted rabbit is crossed with a solid colored rabbit, all the offspring will be spotted. When the F1 rabbits interbreed, they produce 31 spotted rabbits and 11 solid colored rabbits. How many of the F2 rabbits would you expect to be homozygous for coat condition? How would you make a Punnett Square explaining the problem?

Thanks again!

Answer 1

This can throw you off because it the "spotted" (S) is the dominant trait (the solid (s) is probably white [recessive]). This is determined from the first sentence AND the F1 cross:

Look at what happens in the F1 cross. You get a 3:1 ratio (31 spotted:11solid). If you do a Punnet Square with heterozygous parents (Ss x Ss) you get genotypes 1SS:2Ss:1ss. The phenotypes would be 3 spotted : 1 solid. If the spotted parent was heterozygous (Ss), half of the F1 would be spotted, half solid. Therefore, you can say that spotted is the dominant condition.

So knowing that the F1 rabbits are heterozygous, make your square:

__S___s__
S :___ :____:
s :____:____:

How many of the F2 are homozygous? (HINT remember homozygous means both letters have the same case - it doesn't specify dominant or recessive)