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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3:13 minutes

Problem 10b

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= 1, w_Aa= 0.95, w_aa= 0.9

Verified step by step guidance

Step 1: Understand the problem. The question involves calculating allele frequencies after one generation under selection. The given fitness values (wAA=1, wAa=0.95, waa=0.9) represent the relative reproductive success of each genotype. The initial allele frequencies are p=0.7 for allele A and q=0.3 for allele a. Codominance means heterozygotes (Aa) have a distinct phenotype.

Step 2: Calculate the genotype frequencies before selection using Hardy-Weinberg equilibrium. The formulas are:

f_{AA} =p

², fAa=2pq, and faa=q². Substitute p=0.7 and q=0.3 into these equations.

Step 3: Apply selection to the genotype frequencies. Multiply each genotype frequency by its respective fitness value (wAA, wAa, waa). The formulas are:

f_{AA}'= f_{AA} ×w AA, f_{Aa}'= f_{Aa} ×w Aa, and f_{aa}'= f_{aa} ×w aa . This adjusts the frequencies based on fitness.

Step 4: Normalize the adjusted genotype frequencies to ensure they sum to 1. Calculate the total fitness of the population (W) using the formula:

W= f_{AA}'+ f_{Aa}'+ f_{aa}'

. Then divide each adjusted genotype frequency by W to obtain the normalized frequencies.

Step 5: Calculate the new allele frequencies after selection. Use the formulas:

p'= f_{AA}'+0.5× f_{Aa}'

and

q'= f_{aa}'+0.5× f_{Aa}'

. These formulas account for the contribution of each genotype to the allele pool.

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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 genetic variation and evolutionary dynamics within a population.

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=1, wAa=0.95, waa=0.9) indicate how well each genotype can survive and reproduce. This concept is essential for understanding how natural selection influences allele frequencies over generations.

Hardy-Weinberg Principle

The Hardy-Weinberg Principle provides a mathematical framework for understanding genetic variation in a population under ideal conditions. It states that allele and genotype frequencies will remain constant from generation to generation in the absence of evolutionary influences. This principle helps in predicting how allele frequencies change when selection pressures, like those indicated by fitness values, are applied.

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