In a population of flowers growing in a meadow, C₁ and C₂ are autosomal codominant alleles that control flower color. The alleles are polymorphic in the population, with f (C₁) = 0.80 and f (C₂) = 0.20. Flowers that are C₁C₁ are yellow, orange flowers are C₁C₂, and C₂C₂ flowers are red. A storm blows a new species of hungry insects into the meadow, and they begin to eat yellow and orange flowers but not red flowers. The predation exerts strong natural selection on the flower population, resulting in relative fitness values of C₁C₁ = 0.30, C₁C₂ = 0.60, and C₂C₂ = 1.0.
Assuming random mating takes place among survivors, what are the genotype frequencies in the second generation?

Verified step by step guidance

1. Step 1: Understand the problem. The alleles C₁ and C₂ are codominant, meaning heterozygotes (C₁C₂) express a phenotype distinct from either homozygote (C₁C₁ or C₂C₂). The relative fitness values indicate how well each genotype survives under the selective pressure of predation. We need to calculate the genotype frequencies in the second generation after selection and random mating.
2. Step 2: Calculate the post-selection genotype frequencies. Multiply the initial genotype frequencies by their respective relative fitness values to account for survival. Let p = f(C₁) = 0.80 and q = f(C₂) = 0.20. The initial genotype frequencies are: f(C₁C₁) = p², f(C₁C₂) = 2pq, and f(C₂C₂) = q². After selection, the frequencies become: f'(C₁C₁) = p² × 0.30, f'(C₁C₂) = 2pq × 0.60, and f'(C₂C₂) = q² × 1.0.
3. Step 3: Normalize the post-selection frequencies. To ensure the frequencies sum to 1, divide each post-selection frequency by the total sum of all post-selection frequencies. The normalization factor is: Total = f'(C₁C₁) + f'(C₁C₂) + f'(C₂C₂). The normalized frequencies are: f''(C₁C₁) = f'(C₁C₁) / Total, f''(C₁C₂) = f'(C₁C₂) / Total, and f''(C₂C₂) = f'(C₂C₂) / Total.
4. Step 4: Use the normalized frequencies to calculate allele frequencies in the survivors. The allele frequencies are derived from the genotype frequencies: f(C₁) = f''(C₁C₁) + 0.5 × f''(C₁C₂), and f(C₂) = f''(C₂C₂) + 0.5 × f''(C₁C₂). These frequencies represent the alleles available for random mating in the second generation.
5. Step 5: Apply the Hardy-Weinberg principle to predict genotype frequencies in the second generation. Assuming random mating, the genotype frequencies are calculated as: f(C₁C₁) = f(C₁)², f(C₁C₂) = 2 × f(C₁) × f(C₂), and f(C₂C₂) = f(C₂)². These are the genotype frequencies in the second generation.

Key Concepts

Codominance

Codominance is a genetic scenario where two different alleles at a locus are both expressed in the phenotype of a heterozygote. In this case, the alleles C1 and C2 produce distinct flower colors when present together (C1C2 results in orange flowers), illustrating how both alleles contribute to the observable traits.

Natural Selection

Natural selection is the process by which certain traits become more or less common in a population due to the survival and reproductive success of individuals with those traits. In this scenario, the predation of yellow and orange flowers leads to a decrease in their frequencies, favoring the survival of red flowers (C2C2), which influences the genotype frequencies in subsequent generations.

Genotype Frequencies

Genotype frequencies refer to the proportion of different genotypes in a population. After natural selection, the remaining individuals will have altered frequencies of C1C1, C1C2, and C2C2 genotypes, which can be calculated using the relative fitness values and the Hardy-Weinberg principle, assuming random mating among survivors.