Genetic drift #11 Flashcards
What is random genetic drift?
Random genetic drift is the random changes in allele frequencies over generations in the absence of selection. It is caused by chance events of survival, reproduction, and inheritance, causing evolution. Chance fluctuations in allele frequencies result from random sampling of gametes for the next generation.
What happens during segregation during meiosis in heterozygotes?
During segregation during meiosis, when heterozygous, only one of the two alleles is passed to each gamete with a 50% chance that one of your alleles leaves no descendants.
What is the effect of genetic drift on genetic variation?
Genetic drift causes a loss of genetic variation (fixation: p/q = 0 can be fast, and without natural selection). However, variation can be reintroduced by mutation.
What is the role of genetic drift in causing populations to diverge?
Genetic drift causes populations that are initially identical to diverge because of shuffling of alleles without exchange between each other, leading to random differentiation and eventual speciation.
What are the special cases of genetic drift?
The special cases of genetic drift include bottlenecks, which are events that drastically reduce the size of the population (e.g., environmental disaster, habitat destruction), and founder events, which involve a small number of individuals that represent a small portion of the total gene pool founding a new population.
What is the impact of drift on gene coalescence and population size?
Drift impacts populations when we go back in time (‘coalesce’). Genes coalesce in the recent past when population size is small, and in the remote past when it’s large. The average time back to the common ancestor of a neutral gene in a diploid is 2Ne generations, where Ne is the effective population size.
What is a gene tree?
A gene tree is a diagrammatic representation of the ancestry of a gene. When lineages converge back in time, they coalesce to a most recent common ancestor.
What is the effect of drift on deleterious alleles?
Drift can result in the fixation of deleterious alleles, which can be harmful to the population.
What is the difference between drift and natural selection?
Drift is random and unbiased, while natural selection favors one advantageous allele over another. Drift has a larger effect in small populations, while selection has a larger effect in large populations.
