Question

In the following tetrahybrid cross AaBbCcDd x AaBbCcDd what proportion of the F₂ offspring would be expected to be phenotypically ABCD?

a) 81/256
b) 1/256
c) 1/2
d) 9/256

Answer 1

The proportion of F₂ offspring in a tetrahybrid cross AaBbCcDd that are expected to be phenotypically ABCD is 81/256, calculated using the product rule for each dominant phenotype probability.

Step-by-step explanation:

In a tetrahybrid cross of AaBbCcDd × AaBbCcDd, you were asking for the proportion of F₂ offspring with the dominant phenotype for all four loci (ABCD). To find this, we can use the product rule in genetics. We calculate the probability of having a dominant phenotype for each gene locus (either homozygous dominant or heterozygous) and multiply these probabilities together. Since each dominant phenotype occurs with a probability of 3/4 (either 1/4 homozygous dominant + 1/2 heterozygous), the overall proportion is 3/4 × 3/4 × 3/4 × 3/4, which equals 81/256. Thus, the proportion of F₂ offspring expected to be phenotypically ABCD is 81/256.