Lecture 5: Genetic Drift (and Inbreeding) Flashcards
Natural Selection acts on __or __ __ in a population. without it, Natural Selection cannot occur
genetic or epigenetic variation
What is Natural Selection?
Process where organisms with advantageous traits are more likely to survive and reproduce, passing on those traits to future generations.
What generates genetic variation through random changes in the DNA sequence?
Mutation
What modifies gene expression without changing the DNA sequence itself?
Epigenetic modification
What causes fluctuations in allele frequencies and can reduce genetic variation in small populations?
Genetic drift
What is Migration in the context of genetics?
Movement of individuals between populations.
How can Migration act as a homogenizing force?
By reducing differences between populations through gene flow.
What can happen to a population with high migration rates regarding Hardy-Weinberg equilibrium?
It may go out of Hardy-Weinberg equilibrium.
What impact does Immigration (inward movement) have on genetic variation within a population?
It could introduce new genetic variation.
How does Emigration (outward movement) affect genetic variation within a population?
It could reduce genetic variation by removing individuals from the population.
Who was Sewall Wright and what did he study?
Sewall Wright studied agricultural stocks, such as cows, and was particularly interested in small, inbred populations.
What genetic mechanisms did Sewall Wright regard as particularly important?
Inbreeding and Genetic Drift.
What could Genetic Drift and Inbreeding generate according to Sewall Wright?
new gene interactions
What did Sewall Wright consider as the main substrate for selection?
New gene interactions, particularly those caused by epistasis through new recombinations.
What is Random Genetic Drift?
Changes in allele frequency from one generation to the next due to chance (sampling error).
Is Random Genetic Drift adaptive or non-adaptive?
Non-adaptive.
Did Charles Darwin recognize genetic drift as an evolutionary mechanism?
No.
- happens when populations are limited in size, violating HW assumption of infinite population size
- Changes in allele frequencies due to random chance events in small populations.
Genetic drift
Under what condition does Genetic Drift occur?
Limited population size, violating the Hardy-Weinberg assumption of infinite population size.
- During the Evolutionary Synthesis, Sewall Wright focused more on importance of __ __, whereas Fisher focused on __ __
- Genetic Drift
- Natural Selection
- Shortly after the Evolutionary Synthesis many focused on __ to the point of assuming that most phenotypes were the result of Natural Selection
- selection
- Emphasis on Genetic Drift resurged in the 1970s, 80s with __ “ __ __ “
Kimura’s “Neutral Theory”
Then in the 2000s and 2010s interest in Selection increased with the ability to detect signatures of Natural Selection in __ __ __
genome sequence data
How does population size influence the impact of chance events on allele frequencies?
In large populations, chance events cancel each other out; in small populations, random differences in reproductive success become more significant.