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

Allelic Frequency Changes

Genetics

21. Population Genetics

Allelic Frequency Changes

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2:05 minutes

Problem 5

Textbook Question

Thinking creatively about evolutionary mechanisms, identify at least two schemes that could generate allelic polymorphism in a population. Do not include the processes described in the answer to Problem 4.

Verified step by step guidance

Step 1: Understand the concept of allelic polymorphism, which refers to the presence of two or more alleles at a locus within a population, contributing to genetic diversity.

Step 2: Recall that evolutionary mechanisms generating allelic polymorphism include mutation, natural selection, gene flow, genetic drift, and recombination, but exclude those mentioned in Problem 4 as per the instructions.

Step 3: Consider mutation as one scheme: random changes in DNA sequences introduce new alleles into the population, increasing allelic variation over time.

Step 4: Consider balancing selection as another scheme: this includes mechanisms like heterozygote advantage or frequency-dependent selection, which maintain multiple alleles in the population by favoring genetic diversity.

Step 5: Summarize that both mutation (introducing new alleles) and balancing selection (maintaining multiple alleles) are key evolutionary schemes that can generate and sustain allelic polymorphism in populations.

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Key Concepts

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

Allelic Polymorphism

Allelic polymorphism refers to the presence of two or more different alleles at a gene locus within a population. This genetic variation is essential for evolution and adaptation, as it provides the raw material for natural selection to act upon.

Balancing Selection

Balancing selection is an evolutionary mechanism that maintains multiple alleles in a population by providing a selective advantage to heterozygotes or through frequency-dependent selection. This process helps preserve genetic diversity and can generate stable allelic polymorphism.

Mutation and Gene Flow

Mutation introduces new alleles into a population by altering DNA sequences, while gene flow involves the transfer of alleles between populations through migration. Both mechanisms increase genetic variation and can contribute to the generation and maintenance of allelic polymorphism.

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Textbook Question

In a population, what is the consequence of inbreeding? Does inbreeding change allele frequencies? What is the effect of inbreeding with regard to rare recessive alleles in a population?

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Write a short essay describing the roles of mutation, migration, and selection in bringing about speciation.

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Identify and describe the evolutionary forces that can cause allele frequencies to change from one generation to the next.

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Textbook Question

Describe how natural selection can produce balanced polymorphism of allele frequencies through selection that favors heterozygotes.

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Textbook Question

Genetic drift, an evolutionary process affecting all populations, can have a significant effect in small populations, even though its effect is negligible in large populations. Explain why this is the case.

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Textbook Question

Over the course of many generations in a small population, what effect does random genetic drift have on allele frequencies?

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Textbook Question

Catastrophic events such as loss of habitat, famine, or overhunting can push species to the brink of extinction and result in a genetic bottleneck. What happens to allele frequencies in a species that experiences a near-extinction event, and what is expected to happen to allele frequencies if the species recovers from near extinction?

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Textbook Question

George Udny Yule was wrong in suggesting that an autosomal dominant trait like brachydactyly will increase in frequency in populations. Explain why Yule was incorrect.