Question

In the cross RrTt × rrt:

Options

• all the offspring will be tall with red fruit

• 75% (3/4) will be tall with red fruit

• 50% (1/2) Will be tall with red fruit

• 25% (1/4) will be tall with red fruit

Answer 1

25% (1/4) will be tall with red fruit

Explanation:

The cross is RrTt × rrtt, where:

• R (red fruit) is dominant over r (yellow fruit),
• T (tall) is dominant over t (dwarf).

Possible gametes from RrTt are RT, Rt, rT, rt. Possible gametes from rrtt are only rt.

Offspring genotypes from the cross:

• RT × rt = RrTt (tall, red fruit)
• Rt × rt = Rrtt (dwarf, red fruit)
• rT × rt = rrTt (tall, yellow fruit)
• rt × rt = rrtt (dwarf, yellow fruit)

Counting offspring with tall and red fruit (R_T_): Only RrTt (1 out of 4) will be tall with red fruit. So the probability is 1/4 or 25%.