Population genetics Flashcards
what is population genetics?
study of genes and genotypes in a population
what is a gene pool?
all of the alleles of every gene in a given population
what is population?
group of individuals of the same species that occupy the same environment and can interbreed with one another
what is polymorphism?
two or more variations for a given character due to two or more alleles that influence phenotype
what is polymorphic gene?
two or more alleles
what is monomorphic gene?
predominantly single allele
what is Single nucleotide polymorphisms (SNPs)?
smallest and most common type of genetic change in a gene
what is the formula for allele frequency?
Number of copies of a specific allele in a population / Total number of all alleles for that gene in the population
What is the formula for genotype frequency?
Number of individuals with a particular genotype in a population / Total number of individuals in the population
what is the Hardy-Weinberg equilibrium?
It predicts that allele and genotype frequencies will remain the same, generation after generation, provided that a population is in equilibrium
how can a population be in equilibrium?
To be in equilibrium, population must not be affected by evolutionary mechanisms that change allele and genotype frequencies.
what are the conditions for Hardy-Weinberg equilibrium?
- No new mutations occur
- No natural selection occurs
- The population is so large that allele frequencies do not change due to random chance
- No migration occurs between different populations
- Random mating occurs
If frequencies are not in equilibrium, an evolutionary mechanism is at work. True or False?
True
what is microevolution?
changes in a population’s gene pool from generation to generation.
what are the causes of change in a population’s gene pool?
- Introduction of new genetic variation (mutations, gene duplication, horizontal gene transfer)
- Evolutionary mechanisms that alter the prevalence of an allele or genotype (natural selection, genetic drift, migration, nonrandom mating)
what is natural selection?
the process in which beneficial traits that are heritable become more common in successive generations
what is reproductive success?
likelihood of an individual contributing fertile offspring to the next generation
the two categories of traits of associated with reproductive success?
ability to find a mate and ability to produce viable gametes and offspring
what is fitness?
relative likelihood that a genotype will contribute to the gene pool of the next generation as compared to other genotypes. Measure of reproductive success.
what is mean fitness of population?
average reproductive success of members of a population
list the 4 natural selection patterns?
- Directional selection
- Stabilizing selection
- Disruptive/Diversifying selection
- Balancing selection
what is directional selection?
Individuals at one extreme of a phenotypic range have greater reproductive success in a particular environment. It is initiated by new allele with higher fitness introduced and prolonged environmental change
what is stabilizing selection?
favours the survival of individuals with intermediate phenotypes. Too many eggs and offspring die due to lack of care and food, too few eggs do not contribute enough to next generation
what is Disruptive/Diversifying selection?
favours the survival of two or more genotypes that produce different phenotypes, likely to occur in populations that occupy heterogenous environments and members of the population can fully interbreed
what is balancing selection?
maintains genetic diversity
what is balanced polymorphism?
Two or more alleles are kept in balance and maintained in a population over the course of many generations
two common ways of balanced polymorphism?
- for a single gene, heterozygote favored
- negative frequency-dependent selection
what is sexual selection?
Directed at certain traits of sexually reproducing species that make it more likely for individuals to find or choose a mate and/or engage in successful mating
what is sexual dimorphism?
significant difference between the morphologies of the two sexes within a species
what is intrasexual selection?
males directly compete for mating opportunities or territories, between members of the same sex.
what is intersexual selection?
Members of one sex, usually
females, choose their mates
from individuals of the other
sex based on desirable
characteristics, often results in showy characteristics for males
what are the benefits of sexual selection for males and females?
Males can produce more offspring by increasing the number of mates, females can increase fitness by choosing good mates
what is genetic drift?
A change in genetic variation from generation to generation due to random chance.
what is bottleneck?
Population reduced dramatically and then rebuilds, randomly eliminates members.
what is founder effect?
small group of individuals separates from a larger population and establishes a new colony
neutral variation
much of the genetic variation seen in natural populations is caused by genetic drift
neutral theory of evolution?
Members of one sex, usually
females, choose their mates
from individuals of the other
sex based on desirable
characteristics, sequencing data supports this idea
what is gene flow?
occurs when individuals migrate between populations having different allele frequencies
Migration
tends to reduce differences in allele frequencies between two populations, tends to enhance genetic diversity within a population.
random mating
individuals choose their mates irrespective of their genotypes and phenotypes
forms of nonrandom mating
- Assortative/disassortative mating
- Inbreeding
assortative mating
individuals with similar phenotypes are more likely to mate, increases the proportion of homozygotes
disassortative mating
dissimilar phenotypes mates preferentially, favors heterozygosity
Inbreeding
choice of mate based on genetic history, increases likelihood the individual will be homozygous
