Biology:

A homozygous round seeded plant is crossed with a homozygous wrinkled seeded plant.
What are the genotypes of the parents?
What percentage of the offspring will also be homozygous?
What is will the punnet square look like?

1 answer

In this scenario, you are dealing with a classic Mendelian genetics problem concerning seed shape. In pea plants, round seeds (R) are typically dominant over wrinkled seeds (r).

1. Genotypes of the Parents

  • The homozygous round-seeded plant has the genotype RR.
  • The homozygous wrinkled-seeded plant has the genotype rr.

2. Percentage of Offspring That Will Be Homozygous

When you cross RR (homozygous round) with rr (homozygous wrinkled), all offspring will inherit one allele from each parent. The offspring will all have the genotype Rr (heterozygous round).

  • Genotype of the offspring: 100% Rr (heterozygous)
  • Since none of the offspring are homozygous (RR or rr), the percentage of homozygous offspring is 0%.

3. Punnett Square

The Punnett square for this cross (RR x rr) would look as follows:

| | R | R | |-----|------|------| | r | Rr | Rr | | r | Rr | Rr |

Summary

  • Genotypes of Parents: RR (round) and rr (wrinkled)
  • Percentage of Homozygous Offspring: 0%
  • Punnett Square: All cells show Rr (100% Rr, heterozygous round).

Thus, all offspring will be heterozygous round-seeded plants.