Question

The variation of kernel color in corn plants is an inherited trait. R is the dominant allele for red kernels in a corn plant and r is the recessive allele for yellow kernels.
What is the probability that a corn plant with the genotype Rr crossed with a corn plant rr will have offspring with the genotype rr? Express your answer as a fraction using numerals for numbers and / for the fraction bar. Do not include spaces.

Answer 1

The answer is 1/2.

If:
R - the dominant allele for red kernels
r - the recessive allele for yellow kernels

Then:
RR - dominant homozygote
Rr - heterozygote
rr - recessive homozygote

The cross Rr x rr will result in 1/2 of offspring with red kernels (Rr) and 1/2 of offspring with yellow kernels (rr):
Parental generation:      Rr      x      rr
Offspring generation:  Rr    Rr     rr      rr
So, there are 2 out of 4 Rr offspring (2/4 = 1/2) and 2 out of 4 rr offspring (2/4 = 1/2).