Question

A plant with round seeds is crossed with another plant with round seeds. Round are dominant over oval seeds. When two heterozygous round-seeded plants are crossed, what is expected of their offspring assuming random chromosome segregation?

A)
The oval-shaped plant will appear 50% of the time.
B)
The round-shaped plant will appear 100% of the time.
C)
The oval-shaped plant will most likely appear 75% of the time.
D)
The round-shaped plant will most likely appear 75% of the time.

Answer 1

The correct answer would be D) The round-shaped plant will most likely appear 75% of the time.

Let R and r be the dominant and recessive alleles of a gene responsible for the shape of the seeds in a plant.

R results in the production of round-shaped seeds in a plant whether present in the homozygous or heterozygous condition.

r being recessive allele express itself only in a homozygous condition which results in the production of oval-shaped seeds in a plant.

Now the genotype of the round-seeded parent plants would be Rr. They will produce two types of gametes R and r.

The monohybrid cross would result in the production of offspring with three possible combinations of alleles RR, Rr, and rr in 1:2:1.

Three out of four offspring would show a dominant trait that is, round shape seeds, while only one out of four would show a recessive trait that is, oval-shaped seeds.

Thus, when two heterozygous round-seeded plants are crossed then the round-shaped plant will most likely appear 75% (3 out of 4 times) of the time.

Answer 2

The round-shaped plant will most likely appear 75% of the time is expected of their offspring assuming random chromosome segregation.