Question

Consider a gene with four alleles A1, A2, A3, and A4. If the cross A1A2 × A3A4 yields two offspring, what is the probability that both of them have the same genotype?

Answer 1

There are 4 possible genotypes among any offspring (2 possible alleles from either A1 or A3, and 2 possible alles from either A2 or A4; 2*2=4), all of which are equally likely to occur with probability 1/4.

The probability that 2 offspring have the same genotype is (1/4)^2 = 1/16.