Podcast
Questions and Answers
Which process is specifically known to decrease genetic diversity within populations?
Which process is specifically known to decrease genetic diversity within populations?
- Recombination
- Natural selection
- Genetic drift (correct)
- Mutation
What metric measures the fraction of individuals that are heterozygous across gene loci?
What metric measures the fraction of individuals that are heterozygous across gene loci?
- Polymorphism (P)
- Allelic diversity (A)
- Heterozygosity (H) (correct)
- Genetic variance (G)
Which factor maintains genetic variation through the reintroduction of less fit types?
Which factor maintains genetic variation through the reintroduction of less fit types?
- Natural selection
- Mutation-selection balance (correct)
- Heterozygote advantage
- Genetic drift
Which of the following has the potential to both increase and decrease genetic diversity?
Which of the following has the potential to both increase and decrease genetic diversity?
What term describes the proportion of gene loci with two or more alleles in a population?
What term describes the proportion of gene loci with two or more alleles in a population?
Which school of thought emphasizes the importance of balancing selection in maintaining genetic variation?
Which school of thought emphasizes the importance of balancing selection in maintaining genetic variation?
Which process is NOT directly mentioned as increasing genetic diversity?
Which process is NOT directly mentioned as increasing genetic diversity?
The principle behind the heterozygote advantage suggests that which individuals have higher fitness?
The principle behind the heterozygote advantage suggests that which individuals have higher fitness?
What does the selection response indicate about polygenic quantitative traits?
What does the selection response indicate about polygenic quantitative traits?
Why is it challenging to conduct comparative studies on traits?
Why is it challenging to conduct comparative studies on traits?
What fundamental question do Lewontin's allozyme studies aim to address?
What fundamental question do Lewontin's allozyme studies aim to address?
What advantage do enzyme polymorphism studies provide?
What advantage do enzyme polymorphism studies provide?
What type of genes can be identified through protein electrophoresis?
What type of genes can be identified through protein electrophoresis?
What was a significant outcome of the first allozyme studies?
What was a significant outcome of the first allozyme studies?
What do allozymes represent?
What do allozymes represent?
What does the presence of high genetic variation suggest for natural populations?
What does the presence of high genetic variation suggest for natural populations?
What is the primary focus of early quantitative genetic evidence?
What is the primary focus of early quantitative genetic evidence?
What method is commonly used to study genetic variation in populations?
What method is commonly used to study genetic variation in populations?
What does the selection response for bristle number in fruit flies demonstrate?
What does the selection response for bristle number in fruit flies demonstrate?
What happens when selection is relaxed in maize populations?
What happens when selection is relaxed in maize populations?
What potential explanation exists for evolutionary responses in continuous traits?
What potential explanation exists for evolutionary responses in continuous traits?
What is a common outcome of artificial selection based on controlled breeding?
What is a common outcome of artificial selection based on controlled breeding?
Which of the following describes the relationship between many underlying genes and phenotypes?
Which of the following describes the relationship between many underlying genes and phenotypes?
What is the likely effect of initially rare and deleterious alleles when selection resumes?
What is the likely effect of initially rare and deleterious alleles when selection resumes?
Which factor contributes to the maintenance of genetic variation in natural populations?
Which factor contributes to the maintenance of genetic variation in natural populations?
What is a consequence of negative selection in the context of genetic variations?
What is a consequence of negative selection in the context of genetic variations?
Which statement accurately describes selectively neutral variation?
Which statement accurately describes selectively neutral variation?
What is the role of balancing selection in maintaining genetic diversity?
What is the role of balancing selection in maintaining genetic diversity?
Which of the following describes the mutation-selection balance concept?
Which of the following describes the mutation-selection balance concept?
In the context of genetic variation, what does the term 'frequency-dependent selection' imply?
In the context of genetic variation, what does the term 'frequency-dependent selection' imply?
What is a significant consequence of the population bottleneck during the domestication of maize?
What is a significant consequence of the population bottleneck during the domestication of maize?
What does the Neutral Theory suggest about molecular variation?
What does the Neutral Theory suggest about molecular variation?
What is the primary factor that distinguishes changes in the genetic code that affect protein from those that do not?
What is the primary factor that distinguishes changes in the genetic code that affect protein from those that do not?
Which of the following describes mutation-selection balance in a population?
Which of the following describes mutation-selection balance in a population?
How does the DNA sequence variation in natural populations generally manifest?
How does the DNA sequence variation in natural populations generally manifest?
What effect did selection on certain genes have on maize's DNA diversity compared to teosinte?
What effect did selection on certain genes have on maize's DNA diversity compared to teosinte?
What is the DNA diversity comparison between maize and its wild ancestor, teosinte?
What is the DNA diversity comparison between maize and its wild ancestor, teosinte?
What is a major difference between maize and teosinte at the genetic level?
What is a major difference between maize and teosinte at the genetic level?
What does DNA sequence diversity indicate concerning bases in natural populations?
What does DNA sequence diversity indicate concerning bases in natural populations?
Which statement best describes the genetic makeup of maize as a result of domestication?
Which statement best describes the genetic makeup of maize as a result of domestication?
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Study Notes
Forces Influencing Genetic Diversity and Evolution
- Mutation, recombination, and migration tend to increase genetic diversity.
- Genetic drift tends to decrease genetic diversity.
- Natural selection can increase or decrease genetic diversity.
Measuring Genetic Variation
- Heterozygosity (H): The fraction of heterozygous individuals across gene loci.
- Polymorphism (P): The proportion of gene loci with two or more alleles. A locus can be polymorphic without being heterozygous.
Maintaining Genetic Variation
- Mutation-selection balance: Less-fit types are reintroduced by mutation and subsequently removed by selection.
- Balancing selection: Includes heterozygote advantage, frequency-dependent selection, and fitness varying across space or time.
Early Evidence for Genetic Variation
- Early quantitative genetic studies focused on continuous polygenic traits, using artificial selection experiments across multiple generations.
- These experiments demonstrated heritable variation in fitness-related phenotypes, influenced by many underlying genes. However, information on P and H was often lacking.
Allozyme Electrophoresis and Genetic Variation
- Allozyme gel electrophoresis allowed for measuring the proportion of variable genes (P and H).
- Studies revealed high levels of genetic variation in diverse organisms. Higher than predicted by the classical school of thought.
Interpreting High Genetic Variation
- High genetic variation can be explained by mutation-selection balance, balancing selection, and selectively neutral variation.
Neutral Theory
- The neutral theory suggests that most molecular variation is selectively neutral. Negative selection eliminates detrimental mutations, positive selection fixes beneficial ones, leaving only neutral mutations to contribute to variation.
DNA-Level Genetic Variation Studies
- Direct DNA sequencing provides more precise measurements of genetic differences, distinguishing changes affecting protein function from neutral ones.
DNA Variation Across Organisms
- Significant variation exists in DNA sequences across different organisms, with some having higher levels of polymorphism than others.
DNA Variation in Maize vs. Teosinte
- Domesticated maize exhibits reduced genetic diversity compared to its wild ancestor, teosinte. This is attributed to population bottlenecks during domestication, further compounded by selection on specific genes.
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