Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

21. Population Genetics

Hardy Weinberg

Genetics

21. Population Genetics

Hardy Weinberg

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3:12 minutes

Problem 10d

Textbook Question

Consider a population in which the frequency of allele A is p = 0.7 and the frequency of allele a is q = 0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?
w_AA= 0.8, w_Aa= 1, w_aa= 0.8

Verified step by step guidance

Step 1: Understand the problem. The population has two alleles, A and a, with initial frequencies p = 0.7 and q = 0.3, respectively. The alleles are codominant, meaning the heterozygote (Aa) has a distinct phenotype. Fitness values are given as wAA = 0.8, wAa = 1, and waa = 0.8. We need to calculate the allele frequencies after one generation of selection.

Step 2: Calculate the genotype frequencies before selection using the Hardy-Weinberg principle. The genotype frequencies are: f(AA) = p², f(Aa) = 2pq, and f(aa) = q². Substitute p = 0.7 and q = 0.3 into these equations: f(AA) = (0.7)², f(Aa) = 2(0.7)(0.3), and f(aa) = (0.3)².

Step 3: Adjust the genotype frequencies for selection by multiplying each genotype frequency by its respective fitness value. The adjusted frequencies are: f'(AA) = f(AA) × wAA, f'(Aa) = f(Aa) × wAa, and f'(aa) = f(aa) × waa.

Step 4: Normalize the adjusted genotype frequencies to ensure they sum to 1. Calculate the total fitness of the population (W) as W = f'(AA) + f'(Aa) + f'(aa). Then, divide each adjusted frequency by W to get the post-selection genotype frequencies: f''(AA) = f'(AA)/W, f''(Aa) = f'(Aa)/W, and f''(aa) = f'(aa)/W.

Step 5: Calculate the new allele frequencies from the post-selection genotype frequencies. The frequency of allele A (p') is given by p' = f''(AA) + 0.5 × f''(Aa), and the frequency of allele a (q') is given by q' = f''(aa) + 0.5 × f''(Aa). These are the allele frequencies after one generation of selection.

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Key Concepts

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

Allele Frequency

Allele frequency refers to how often a particular allele appears in a population relative to the total number of alleles for that gene. In this case, the frequencies of alleles A and a are given as p=0.7 and q=0.3, respectively. Understanding allele frequencies is crucial for predicting how they may change over generations due to factors like selection, mutation, and genetic drift.

Fitness and Selection

Fitness in genetics refers to the reproductive success of an organism relative to others in the population. The given fitness values (wAA=0.8, wAa=1, waa=0.8) indicate how well each genotype can survive and reproduce. This concept is essential for understanding how natural selection can influence allele frequencies over generations, as genotypes with higher fitness will contribute more to the next generation.

Hardy-Weinberg Equilibrium

The Hardy-Weinberg equilibrium is a principle that describes the genetic variation in a population that is not evolving. It provides a baseline to compare actual allele frequencies against expected frequencies under ideal conditions. In this scenario, the deviation from Hardy-Weinberg conditions due to selection pressures can help predict the new allele frequencies after one generation.

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Consider a population in which the frequency of allele A is p = 0.7 and the frequency of allele a is q = 0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?

w_AA= 1, w_Aa= 0.99, w_aa= 0.98

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Textbook Question

w_AA= 1, w_Aa= 0.95, w_aa= 0.9

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Textbook Question

Consider a population in which the frequency of allele A is p=0.7 and the frequency of allele a is q=0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?

wAA=1, wAa=0.9, waa=0.8

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Consider a population in which the frequency of allele A is p = 0.7 and the frequency of allele a is q = 0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?wAA = 0.8, wAa = 1, waa = 0.8

Key Concepts

Allele Frequency

Fitness and Selection

Hardy-Weinberg Equilibrium

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Consider a population in which the frequency of allele A is p = 0.7 and the frequency of allele a is q = 0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?
w_AA= 0.8, w_Aa= 1, w_aa= 0.8