Question

A gardener crosses tall true-breeding pea plants with short true-breeding ones. Tall plants are dominant to short ones. He collects the seeds to grow F1 plants and then allows them to self-pollinate to form an F2 generation. Which of the following describes the traits of the offspring correctly?

Answer 1

The responses given are as follows;
a) Three–fourths of the F1 and one–half of the F2 plants will be tall.
b) All of the F1 and three–fourths of the F2 plants will be tall.
c) Three–fourths of the F1 and all of the F2 plants will be tall.

Let’s name tall as T and short as t
Since both are true breeding plants
Tall plants have the genotype TT and short plants have the genotype tt
Tall plants will make gametes of type T only
Short plants make gametes of type t only
After cross breeding the offspring would all be of genotype Tt as they’re made of T and t gametes
F1 generation formed have the genotype Tt
Since T is dominant all F1 plants are tall
When F1 self pollinates
F1 * F1
Tt *Tt
Gametes are
T t T t
F2 population offspring genotypes are as follows;
TT -1/4 tall
Tt -1/4 tall
Tt -1/4 tall
tt - 1/4 short
3/4 of the plants are tall
Remaining 1/4 is short

Therefore response b is correct
All f1 plants are tall and 3/4 of f2 plants are tall