A plant with genotype $AaBbCc$ is selfed. Assuming independent assortment and complete dominance, what proportion of the offspring will have the phenotype $ABC$?

Solution

1. For each gene pair $Aa$, $Bb$, and $Cc$, the probability of the dominant phenotype is $3/4$.
2. Since the genes assort independently, the probability of the combined phenotype $ABC$ is $(3/4)\times (3/4)\times (3/4)$.
3. Calculating the product gives $27/64$.
4. Hence the answer is (A).