Question

In pea plants, tallness (T) is dominant to shortness (t). What is the predicted genotypic ratio of the offspring if a homozygous short plant is crossed with a heterozygous tall plant? a. 25 percent Tt, 75 percent tt b. 25 percent tall, 75 percent short c. 50 percent Tt, 50 percent tt d. 50 percent tall, 50 percent short

Answer 1

First, to answer this question, you need to draw a Punnett square. So you put the homozygous short alleles (tt) on top of the square, and the heterozygous tall alleles (Tt) on the left side of the square (or vice versa, it doesn't really matter).

When you create the Punnett Square, you then perform the cross between the two plants' alleles. I cross t with T and that gives me Tt. Same with the next one, t and T becomes Tt. Then, I cross t with t and that gives me tt. Same with the next one, t and t becomes tt.

So, the answer here would then be c. 50 percent Tt, 50 percent tt. You might say, well, couldn't answer d also work? Answer d could only work if the question was asking for the phenotypic ratio of the offspring. Then you could say 50% tall, 50% short. But the question asks for the genotypic ratio, so it would instead be c. 50 percent Tt, 50 percent tt.

Hope this helps! 

Answer 2

The correct answer is C) 50 percent Tt, 50 percent tt.