In garden peas, the allele for tall plants is dominant over the allele for short plants. A true-breeding tall plant is crossed with a short plant, and one of their offspring is test crossed. Out of 20 offspring resulting from the test cross, about _______ should be tall.
A) 0
B) 5
C) 10
D) 15
E) 20

Question

Quizplus · Accepted Answer

When a true-breeding tall plant (TT) is crossed with a short plant (tt), their offspring (Tt) will all be tall because the dominant allele (T) masks the recessive allele (t). When one of their offspring (Tt) is test crossed with a short plant (tt), half of the resulting offspring will be tall (Tt) and the other half will be short (tt) because the parent Tt plant can pass on either the dominant or recessive allele. Therefore, out of 20 offspring resulting from the test cross, about 10 should be tall.

In Garden Peas, the Allele for Tall Plants Is Dominant