Which types of phenotypic ratios are likely to occur in testcrosses when dealing with two gene pairs for which all the genotypic combinations are of equal viability?
A) 9:3:3:1, 27:9:9:9:3:3:3:1
B) 1:2:1, 3:1
C) 1:1:1:1
D) 12:3:1, 9:7
E) 2:3, 1:2

Question

Quizplus · Accepted Answer

When all genotypic combinations are of equal viability and we are dealing with two gene pairs, we can expect a phenotypic ratio of 1:1:1:1 in the testcross progeny. This is because each gamete from the heterozygous parent can combine with any gamete from the homozygous recessive parent to produce four equally viable genotypic combinations, resulting in an equal distribution of phenotypes in the offspring. Therefore, option C is the best choice as it corresponds to a 1:1:1:1 ratio.

Which Types of Phenotypic Ratios Are Likely to Occur in Testcrosses