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Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 20 - Population Genetics and Evolution at the Population, Species, and Molecular LevelsProblem 26a
Chapter 20, Problem 26a

Assume that the flower population described in the previous problem undergoes a different pattern of predation. Flower-color determination and the starting frequencies of C₁ and C₂ are as described above, but the new insects attack yellow and red flowers, not orange flowers. As a result of the predation pattern, the relative fitness values are C₁C₁ = 0.40, C₁C₂ = 1.0, and C₂C₂ = 0.80.
What are the allele frequencies after one generation of natural selection?

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1
Step 1: Understand the problem. The question involves calculating allele frequencies after one generation of natural selection, given the relative fitness values for three genotypes (C₁C₁, C₁C₂, and C₂C₂). The starting allele frequencies are not explicitly provided but are assumed to be known from the previous problem.
Step 2: Write down the Hardy-Weinberg genotype frequencies before selection. These are calculated using the allele frequencies (p for C₁ and q for C₂) as follows: C₁C₁ = p², C₁C₂ = 2pq, and C₂C₂ = q².
Step 3: Apply the relative fitness values to the genotype frequencies. Multiply each genotype frequency by its respective fitness value: C₁C₁ × 0.40, C₁C₂ × 1.0, and C₂C₂ × 0.80. This gives the adjusted frequencies after selection.
Step 4: Normalize the adjusted frequencies to ensure they sum to 1. Calculate the total adjusted frequency by summing the products from Step 3, and divide each adjusted frequency by this total to obtain the post-selection genotype frequencies.
Step 5: Calculate the new allele frequencies. Use the post-selection genotype frequencies to determine the allele frequencies: p (frequency of C₁) = frequency of C₁C₁ + 0.5 × frequency of C₁C₂, and q (frequency of C₂) = frequency of C₂C₂ + 0.5 × frequency of C₁C₂.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Natural Selection

Natural selection is a fundamental mechanism of evolution where individuals with traits better suited to their environment tend to survive and reproduce more than those with less advantageous traits. In this scenario, the predation pattern affects the survival of flower colors, influencing which alleles (C₁ and C₂) will be passed on to the next generation based on their relative fitness.
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Relative Fitness

Relative fitness refers to the reproductive success of a genotype compared to others in the population. In this case, the fitness values assigned to the genotypes (C₁C₁, C₁C₂, and C₂C₂) indicate how well each genotype survives predation and contributes to the next generation's allele frequencies, with higher values representing greater reproductive success.
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Allele Frequency

Allele frequency is the proportion of a specific allele among all allele copies in a population. After one generation of natural selection, the allele frequencies of C₁ and C₂ will change based on the relative fitness of the genotypes, reflecting the impact of predation on the survival of different flower colors and their corresponding alleles.
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Related Practice
Textbook Question

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?

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Textbook Question

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.

If predation continues, what are the allele frequencies when the second generation mates?

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Textbook Question

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.

What are the equilibrium frequencies of C1 and C2 if predation continues?

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Textbook Question

Assume that the flower population described in the previous problem undergoes a different pattern of predation. Flower-color determination and the starting frequencies of C₁ and C₂ are as described above, but the new insects attack yellow and red flowers, not orange flowers. As a result of the predation pattern, the relative fitness values are C₁C₁ = 0.40, C₁C₂ = 1.0, and C₂C₂ = 0.80.

What are the genotype frequencies among the progeny of predation survivors?

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Textbook Question

Assume that the flower population described in the previous problem undergoes a different pattern of predation. Flower-color determination and the starting frequencies of C₁ and C₂ are as described above, but the new insects attack yellow and red flowers, not orange flowers. As a result of the predation pattern, the relative fitness values are C₁C₁ = 0.40, C₁C₂ = 1.0, and C₂C₂ = 0.80.

What are the equilibrium allele frequencies in the predation environment?

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Textbook Question

ABO blood type is examined in a Taiwanese population, and allele frequencies are determined. In the population, f (Iᴬ) = 0.30, f (Iᴮ) = 0.15, and f (i) = 0.55.f. Assuming Hardy–Weinberg conditions apply, what are the frequencies of genotypes, and what are the blood group frequencies in this population?

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