Question

A pea plant homozygous for the trait of smooth seeds is crossed with a pea plant that is homozygous for the trait of wrinkled seeds. The first generation produces seeds that are all smooth. What percent of the second-generation plants will have smooth seeds when the F1 generation is self-fertilized?

Answer 1

In pea plants, when a homozygous smooth seed plant is crossed with a homozygous wrinkled seed plant, the first generation plants will have all smooth seeds. The percentage of second-generation plants with smooth seeds depends on the genotypes of the first-generation plants. If both parents of the first generation are heterozygous, 75% of the second-generation plants will have smooth seeds.

Step-by-step explanation:

In pea plants, the trait for smooth seeds is dominant over the trait for wrinkled seeds. When a homozygous smooth pea plant is crossed with a homozygous wrinkled pea plant, all the first-generation (F1) plants will have smooth seeds. When these F1 plants are self-fertilized, the second generation (F2) of plants can have smooth or wrinkled seeds. The percentage of F2 plants that will have smooth seeds depends on the genotypes of the F1 plants.

If both parents of the F1 generation are heterozygous (Ss), there is a 3:1 ratio of smooth to wrinkled seeds in the F2 generation. Therefore, 75% of the F2 plants will have smooth seeds.

However, if the F1 generation consists of plants that are homozygous dominant (SS) for the smooth seed trait, all the F2 plants will also be homozygous dominant (SS) and will have smooth seeds.