population genetics & natural selection Flashcards
what evolves and what doesn’t?
population evolves but individuals don’t
what is a population?
localized group of individuals of the same species
what is a gene pool?
the total aggregate of genes (and their alleles) in the population at one time
Why might we need to estimate frequencies of genotypes in a population?
- To predict how many individuals will inherit a genetic disease
- To estimate the proportion of individuals who are ‘carriers’ of a genetic disease
How do we predict genotypes in a population?
Hardy-Weinberg equation
what is the allele frequency equation?
Allele frequency - p + q = 1
what is the allele frequency equation?
Allele frequency - p + q = 1
what is genotypic frequency equation?
Genotypic frequency - p2 + 2pq + q2 = 1
how can we predict genotypic frequency in a population?
through allele frequency
what are p and q in the Hardy-Weinberg equation?
p = frequency of dominant allele
q = frequency of recessive allele
what is pq in the Hardy-Weinberg equation?
heterozygous
what happens in an x-linked trait for females and males?
for an x-linked trait:
- females need to be homozygous recessive to get the disease
- males need just one recessive allele
what are ways allele frequency can change by?
- Non - random mating
- Random Genetic Drift
- Bottleneck Effect
- Founder Effect
- Natural Selection
- Gene Flow or Migration
- Mutation
what are two different types of nonrandom mating?
- assortative mating
- inbreeding
what is assortative mating?
attraction phenotype similar to your own
what is disassortative mating?
goes out of way to not get similar phenotype to your own
what is random genetic drift?
A random change in allele frequencies due to sampling
error over generations
what is inbreeding?
mating with someone who shares similar genes with you
how does genetic drift happen quickly?
genetic drift happens quickly over a small population
what is the bottleneck effect?
original population has equal frequencies but due to some event the population reduces leading to bottle neck effect hence one of the allele is completely gone and the other becomes rare
what is the founder’s effect?
what happens when you establish a new population
what happens when there is a few founding individuals?
can’t capture all of the diversity in the parent population
when is bottleneck effect pronounced?
tiny population
what happens for genetic diversity overtime in the founders effect?
- takes really long time to evolve
- old population has more genetic diversity than new
what is Stabilising Selection?
reduces variation but does NOT change the mean
what is Directional Selection?
changes the mean value towards one extreme
what is Disruptive Selection?
favors the two extremes producing two peaks
what happens before & after in Stabilising Selection?
before
- Medium-sized individuals are favored
- Phenotypes favored by natural selection
after
- Peak gets higher and narrower
what happens before & after in Directional Selection?
before
- Larger individuals favored
after
- Peak shifts in one direction
what happens before & after in Disruptive Selection?
before
- Large and small individuals favored
after
- Two peaks form
what is sexual selection?
- not determined by phenotype’s usefulness just whats valued by other sex
- one phenotype that might be liked by the other sex more than others
what is sexual selection?
- not determined by phenotype’s usefulness just what’s valued by other sex
- one phenotype that might be liked by the other sex more than others
what is Frequency-dependent selection?
Selection depends on how rare or how common a phenotype is
what does being rare do to you?
increases chances of survival and reproduction but once you succeed you become common and are no longer subjected to that selective advantage
what is a cline?
The gradual geographic change in genetic/phenotypic
composition is termed a cline
what is mutation?
Very slow to act and usually disadvantageous, its role is
usually of macroevolutionary proportions
what is Migration?
An individual from another population successfully mates
(i.e. contributes gametes) to the gene pool
what are the advantages of migration?
- brings new alleles
- changes proportions of existing alleles
- changes population size
- makes two populations more similar
