You are given two populations of true-breeding tomato plants with two simple dominant/recessive traits that sort independently. Using the multiplication rule, how many different phenotypic combinations would you expect to see in the F₂ generation? In what phenotypic ratio? A)two, 3:1 B)three, 9:6:1 C)four, 9:3:3:1

Question

Quizplus · Accepted Answer

The multiplication rule states that the probability of two independent events occurring together is the product of their individual probabilities. In this case, we have two independent traits, each with two possible alleles (dominant or recessive), so there are a total of 4 possible allele combinations.
To determine the number of phenotypic combinations, we must consider the possible combinations of these alleles. Using a Punnett square, we can see that these 4 allele combinations will result in 4 possible phenotypes: 
1) homozygous dominant for trait 1 and homozygous dominant for trait 2
2) homozygous dominant for trait 1 and heterozygous for trait 2
3) heterozygous for trait 1 and homozygous dominant for trait 2
4) heterozygous for both traits
Thus, there are 4 possible phenotypic combinations, which will occur in a ratio of 9:3:3:1 (as predicted by the dihybrid cross). Therefore, the best choice is C.

You Are Given Two Populations of True-Breeding Tomato Plants with Two