Lecture 20 Chapter 25 Flashcards
population genetics
○ Study of the distribution and change in frequency of alleles within populations
evolution
change in gene frequency over time in a population
- which leads to speciation and divergence
population
○ A group of interbreeding, sexually reproducing individuals sharing a common set of genes
genetic variation
frequencies affected by evolutionary forces: mutations, gene flow, genetic drift, and natural selection
Hardy-Weinberg Law assumptions and predictions
Allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences - Assumption ○ Population is large, ○ randomly mating, ○ not affected by mutation, ○ No migration ○ No natural selection - Prediction 1 ○ The allelic frequencies of a population do not change - Prediction 2 ○ The genotypic frequencies stabilize
positive assortative mating
a tendency of like individuals to mate
negative assortative mating
a tendency of unlike individuals to mate
Inbreeding
measure of the probability that two alleles are identical by descent
- identical by descent
- -alleles descended from the same copy in a common ancestor e.g hemophillia in royal family
- identical by state
- –alleles that are the same in structure and function but are descended from two different copies in ancestors
inbreeding depression
- increased appearance of lethal and deleterious traits with inbreedng
- inbreeding increases the % of homozygous individuals in the population
outcrossing
the avoidance of mating between related individuals
Natural Selection
○ Differential survival and reproduction of individuals due to differences in phenotype
- frequency of a recessive allele at equilibrium is equal to the square root of the mutation rate divided by the selection coefficient
- the frequency of a dominant allele at equilibrium is equal to the mutation rate divided by the selection coefficient
nonrandom mating
Occurs when the probability that 2 individuals will mate is not the same for all possible pairs of individuals
- occurs when members of 1 biological sex choose mates of the other sex to mate with and compete with members of the same sex for access to members of the opposite sex
mutation
○ A permanent alteration in the DNA sequence that makes up a gene
migration
○ The movement of populations, groups or individuals
In genetic terms, migration enables gene flow: the movement of genes from one population to anoth
genetic drift
The change in the frequency of a gene variant (allele) in a population due to random sampling of organisms
- change in allelic frequency due to chance factors