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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1:55 minutes

Problem 6b

Textbook Question

Consider rare disorders in a population caused by an autosomal recessive mutation. From the frequencies of the disorder in the population given, calculate the percentage of heterozygous carriers:
0.000081

Verified step by step guidance

Identify that the disorder is autosomal recessive, meaning individuals with the disorder are homozygous recessive (genotype aa). The frequency of affected individuals in the population is given as q² = 0.000081.

Calculate the allele frequency of the recessive allele (q) by taking the square root of the frequency of affected individuals: q = √(0.000081).

Determine the frequency of the dominant allele (p) using the relationship p + q = 1, so p = 1 - q.

Calculate the frequency of heterozygous carriers (genotype Aa) using the Hardy-Weinberg principle: 2pq.

Convert the frequency of heterozygous carriers to a percentage by multiplying the result by 100.

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Key Concepts

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

Autosomal Recessive Inheritance

Autosomal recessive disorders occur when an individual inherits two copies of a mutated gene, one from each parent. Carriers have only one mutated allele and typically do not show symptoms. Understanding this inheritance pattern is essential to relate genotype frequencies to disease prevalence.

Hardy-Weinberg Equilibrium

The Hardy-Weinberg principle provides a mathematical framework to relate allele and genotype frequencies in a population under random mating and no evolutionary forces. It allows calculation of carrier frequencies from disease prevalence using the equation p² + 2pq + q² = 1.

Calculating Carrier Frequency from Disease Prevalence

For autosomal recessive disorders, disease prevalence equals q² (homozygous recessive frequency). The carrier frequency is 2pq, where p ≈ 1 for rare alleles. By taking the square root of disease prevalence, q is found, enabling calculation of heterozygous carrier percentage.

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Textbook Question

The ability to taste the bitter compound phenylthiocarbamide (PTC) is an autosomal dominant trait. The inability to taste PTC is a recessive condition. In a sample of 500 people, 360 have the ability to taste PTC and 140 do not. Calculate the frequency of the recessive allele.