Answer:
a) 100% roan
b) 50% red, 50% roan
c) 50% roan, 25% red, 25% white
Explanation:
a) A red bull has the phenotype RR, a white cow has the phenotype rr. Let's do a punnett square. In its gametes, the bull only has R alleles to pass on, and the cow only has r alleles to pass on:
                Bull
            R        R
        r    Rr       Rr
Cow  Â
        r    Rr       Rr
The offspring can only be Rr, so all of them will be roan. (100% roan).
b) A red bull has the phenotype RR, a roan cow has the phenotype Rr. Let's do a punnett square. In its gametes, the bull only has R alleles to pass on, and the cow has an R allele and an r allele to pass on:
                Bull
            R        R
        R    RR       RR
Cow  Â
        r    Rr       Rr
50% of the offspring will be RR, and 50% will be Rr. So half of the offspring will be red, and half will be roan.
c) A roan bull has the phenotype Rr, a roan cow has the phenotype Rr. Let's do a punnett square. In its gametes, the bull has an R allele and an r allele to pass on, and the cow also has an R allele and an r allele to pass on:
                Bull
            R        r
        R    RR       Rr
Cow  Â
        r    Rr       rr
25% of the offspring will be RR, 50% will be Rr, and 25% will be rr. So half of the offspring will be roan, a quarter will be red, (RR), and a quarter will be white (rr)
