The black hair of guinea pigs is produced by a dominant gene $B$ and white by its recessive allele $b$. Unless there is evidence to the contrary, assume that II1 and II4 do not carry the recessive allele. What is the probability of finding the recessive offspring of III 1*111 2?

The correct option is C $\frac{1}{8}$
I 1 and I 2 are heterozygous in natura According to the question II1 and II4 are homozygous dominant in nature which are crossed with II 2 ( bb) and II 3 (Bb) to produce a majority of dominant black coloured guinea pigs. Black coloured guinea pigs can be either homozygous dominant or heterozygous dominant in the F3 generation. However, if we consider the probability of finding the recessive offspring of III 1*111 2 it will be 1/8.

So, the correct option is '1/8'.