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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2:28 minutes

Problem 10a

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.

Verified step by step guidance

Step 1: Understand the problem. The ability to taste PTC is controlled by an autosomal dominant allele (T), while the inability to taste PTC is controlled by a recessive allele (t). We are tasked with calculating the frequency of the recessive allele (t) in the population.

Step 2: Use the Hardy-Weinberg principle to calculate allele frequencies. The Hardy-Weinberg equation is:

p

² + 2pq + q² = 1, where p is the frequency of the dominant allele (T) and q is the frequency of the recessive allele (t). Additionally,

p + q = 1

Step 3: Identify the proportion of individuals who are homozygous recessive (q²). These individuals cannot taste PTC. From the problem, 140 out of 500 people are unable to taste PTC. Calculate q² as

q

² = rac{140}{500}.

Step 4: Solve for q, the frequency of the recessive allele. Since

q = 	ext{sqrt}(q

²), take the square root of the value obtained for q².

Step 5: Verify your understanding. Once q is calculated, you can also determine p (the frequency of the dominant allele) using

p = 1 - q

. This ensures the Hardy-Weinberg equilibrium is satisfied.

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Key Concepts

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

Autosomal Dominance and Recessiveness

Autosomal dominance refers to a pattern of inheritance where only one copy of a dominant allele is needed for the trait to be expressed. In contrast, a recessive trait requires two copies of the recessive allele for expression. In this case, the ability to taste PTC is dominant, while the inability to taste it is recessive.

Hardy-Weinberg Principle

The Hardy-Weinberg principle provides a mathematical framework for understanding allele frequencies in a population at equilibrium. It states that allele and genotype frequencies will remain constant from generation to generation in the absence of evolutionary influences. This principle is essential for calculating allele frequencies, including the recessive allele frequency in the given population.

Allele Frequency Calculation

Allele frequency is the proportion of a specific allele among all allele copies in a population. To calculate the frequency of the recessive allele, we can use the number of individuals expressing the recessive phenotype and apply the Hardy-Weinberg equation. In this scenario, knowing the total number of individuals and the number of tasters allows us to derive the frequency of the recessive allele responsible for the inability to taste PTC.

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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 dominant allele.

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Textbook Question

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