population genetics Flashcards
5 forces of evolution
mutation, selection, non-random mating, gene flow (migration), genetic drift
mutation
change in DNA structure or sequence of a gene, heritable
where does genetic variation come from?
mutation
evolution is ____ in the genetic variation of a population
change
most evolution is ____ in genetic variation
reduction
adaptive evolution (adaptation) occurs only through
natural selection
genotype
set of genes carried by an organism
phenotype
observable characteristic of an organism (morphological structures, developmental process, physiological or behavioral)
4 steps of evolution by natural selection
- Variation (of genotypes and resulting phenotypes)
- Differential Survival/Reproduction (of different phenotypes)
- Differential inheritance (of genotypes underlying successful phenotypes)
- Change in genetic variation
polyphenism
multiple phenotypes arising from a single genotype depending on environmental circumstances (winged vs wingless insects depending on temperature)
reaction norms
different genotypes coding for a range of phenotypes that an individual may develop under various environmental conditions
selection
differential survival and reproductive success
what changes allele frequencies
selection changes allele frequencies in a population, this happens when phenotypes have reproductive success and are heritable. genetic drift and gene flow can also change it over time
the outcome of selection depends upon the relationships of
- relationship between phenotype and fitness
- relationship between phenotype and genotype
absolute fitness
absolute fitness of a genotype is the average lifetime contribution of all individuals with a particular genotype to future gene pools (generations)
what changes genotype frequencies
selection from hardy-weinberg predictions
directional selection
one allele is favored over the other, eventually, the favored allele will be fixed
overdominance (heterozygote advantage)
an allele increases in frequency when rare and decreases in frequency when common
underdominance (homozygote favored)
allele decreases in frequency when rare and increases in frequency when common
if a mutation is ___ selection will act to reduce its frequency
deleterious
how do the forces of evolution cause deviations from HW predictions of genotype frequencies?
by altering allele frequencies in a population, violating the assumptions of random mating, large population size, and no selection. when the forces of evolution are occurring it means a population is evolving and not in genetic equilibrium
in what ways do the forces of evolution change genetic variation within populations
introducing new alleles through mutation, gene flow, and genetic drift causing allele frequency changes in a gene pool
how does population size affect the forces of evolution?
as population size decreases, genetic drift is more impactful. as population size increases, genetic drift is less impactful and natural selection becomes the dominant force
genetic drift
any random change to the allele frequency of a population due to a chance event
what is the equilibrium state of the forces of evolution
The Hardy-Weinberg equilibrium, which is when the frequencies of alleles in a population remain constant from generation to generation
in what ways do the forces of evolution change genetic variation between populations
mutation, gene flow transferring genes between populations, selection of advantageous traits based on the environment
gene flow (migration)
exchange of alleles or genes between different species populations
non-random mating
population does not mate at random and mates with a select number of individuals, the mixing of genotypes is not random
