Drift Flashcards
What is genetic drift and what is the mechanism behind it? Why is drift bound to happen?
Genetic drift is the change in allele frequency due to chance/random sampling or death/survival events not due to genotypic function
What are the expected effects of drift within a population?
Certain alleles will move to fixation while others may be eliminated from the population
What effects the strength of genetic drift?
Poulation size effects the strength of drift, with smaller populations experiencing a greater impact
What are the particular types of historical events that can lead to lasting effects of drifts in otherwise large populations?
Founder effect- a small population is formed by a small number of individuals from a large ancestral population
Bottleneck- one or more generations of small population size prior to regrowth
How does drift work in subdivided populations?
Selection pressures and genetic mutations will be different in the subdivided populations. Random changes will accumulate and while differences within a population decrease, diffences between them will increase
How can we quantify the change in genetic variation due to drift?
Heterozygosity-the expected frequency of heterozygotes within a population
What is the relationship between “effective population size” and “census population size”?
Effective pop size- population expected to match the realized rate of drift
Census pop- actual population size
How can sex ratio affect this?
Males mating with multiple females would be an example. A select number of males pass on genetic information at a much higher rate
How can we quantify the degree of genetic differentiation among subdivided populations?
Fixation index
How does drift operate in large populations?
Takes effect over a much longer period of time
What is neutral genetic variation? What types of mutations are particularly likely to be neutral?
Neutral genetic variation refers to variation with no fitness consequences. Ex height in humans will not effect number of children
How do mutation and drift function to drive neutral nucleotide substitutions?
Mutation-pop size cancels out due to large pops having more alleles and small pops having a higher chance of fixation for each allele
Which population genetic parameters affect this process and why?
of new mutations and probability of each to go to fixation
What does this have to do with the “molecular clock?,” and in general terms, how can predictions from the process be used to detect natural selection in the genome?
Steady predicted rate of change over time, with strong deviations from this expected value being caused by natural selection
