Question

In shorthorn cattle.when a red bull (RR) is crossed with a white cow (rr),all offspring are roan----a spotted,red and white or milky red color.What genotypes are expected from mating a roan bull and roan cow?

Answer 1

Roan offrspring are the offspring produced when a red bull (RR) is crossed with a white cow (rr). Roan refers to the coat colour of certain animals which is a mixture of white and red colour. Roan is a classic example of codominance , in which both the recessive and the dominant traits appear together in the hybrid animals formed. Both the paternal characters appear in the offspring.

When a Roan bull and a Roan cow are mated, the gametes formed are as follows-

Parents- Phenotype Roan X Roan

Genotype Rr X Rr

Gametes R and r

Thus, the offspring formed from the fusion of the above gametes are Red bull (RR), (Roan) Rr and white cow (rr). 25 % of the offspring are red bull, 50% are Roan and 25% are white cow. Thus, the genotypes are RR, Rr and rr.