In a random mating population of Drosophila, 5% of the flies have black bodies (encoded by recessive b) and 95% have brown bodies (encoded by B). Assuming Hardy-Weinberg equilibrium what is the allele frequency of B in the population?
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
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
21. Population Genetics
Hardy Weinberg
Problem 6d
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:
0.01

1
Identify the given frequency of the disorder in the population, which represents the frequency of individuals who are homozygous recessive (q²). In this case, q² = 0.01.
Calculate the allele frequency of the recessive allele (q) by taking the square root of q²: .
Determine the frequency of the dominant allele (p) using the relationship , so .
Calculate the frequency of heterozygous carriers (2pq) using the formula for heterozygotes in Hardy-Weinberg equilibrium: .
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.
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Autosomal Pedigrees
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.
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Hardy Weinberg
Calculating Carrier Frequency from Disease Prevalence
For autosomal recessive disorders, the disease frequency equals q² (homozygous recessive). The carrier frequency is 2pq, where p ≈ 1 for rare alleles. Using the given disease frequency, one can estimate q, then calculate the percentage of heterozygous carriers.
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New Alleles and Migration
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