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Incomplete Dominance

5. In snapdragons, flower color is controlled by incomplete dominance. Two alleles are red (R) and white (r). The heterozygous genotype is expressed as pink.

a. What is the phenotype of a plant with the genotype R R?

b. What is the phenotype of a plant with the genotype rr?

c. What is the phenotype of a plant with genotype Rr?

If you cross a Pink flowered plant with a white flowered plant, what is the probability of getting a pink flowered plant?

Parents: ____________ X _____________

1 answer

In snapdragons, flower color exhibits incomplete dominance, meaning the alleles blend together in heterozygous individuals.

a. The phenotype of a plant with the genotype RR (homozygous red) is red.

b. The phenotype of a plant with the genotype rr (homozygous white) is white.

c. The phenotype of a plant with the genotype Rr (heterozygous) is pink.

To determine the probability of getting a pink flowered plant from a cross between a pink flowered plant (Rr) and a white flowered plant (rr), you can set up a Punnett square:

  • Parents: Pink flowered plant (Rr) X White flowered plant (rr)

The possible combinations from this cross are:

  • R (from Rr) with r (from rr) → Rr (pink)
  • r (from Rr) with r (from rr) → rr (white)

The resulting genotypes from this cross will be:

  • 50% Rr (pink)
  • 50% rr (white)

Thus, the probability of getting a pink flowered plant is 50% or 1 out of 2.

So, to summarize: Parents: Rr X rr
Probability of getting a pink flowered plant: 50%