LO16 Flashcards
Definition: the study of the genetic variability in a population and the evolutionary forces that affect it
population genetics
each population has what?
gene pool
definition: all of the alleles from all of the loci present in a population
gene pool
how is population genetics studied?
By tracking genotype, phenotype, and or allele frequency changes across generations
definition: how often a particular genotype or phenotype or allele occurs divided by the total number of occurances
frequency
frequency is always between which numbers
0 and 1
is gene pool applied to individuals or populations
populations
equation for allele, phenotype ofr genotype frequency
of certain allele/ total # of occurances
definition: the proportion of a particular genotype in a population
genotype frequency
definition: proportion of a particular phenotype in a population
phenotype frequency
definition: the proportion of a particular allele from a given locus in a population
allele frequency
what is occuring in the allele and/or genotype frequencies change over time
evolution
allele and genotype frequencies do not change from generation to generation unless what?
they are affected by outside forces
if a population is large how does sexual reproduction change allele and genotype frequencies?
it doesn’t change
definition: when allele and genotype frequencies are stable for a trait the population is not evolving at the locus
genetic equilibrium
What does the Hardy-Weinberg equation demonstrate?
How populations remain at genetic equilibrium
H-W equation used to calculate what?
expected genotype frequencies
Allele frequency equation
p+q=1
p is what?
frequency of the dominant allele
q is what?
frequency of recessive allele
H-W genotype frequency equation
p^2 + 2pq + q^2 = 1
p^2 is what?
frequency of homozygous dominant genotype
2pq is what?
frequency of heterozygous genotype
q^2 is what?
frequency of homozygous recessive genotype
What happens if the genotype frequencies for a locus conform to H-W equation?
It means that the population is at genetic equilibrium and not evolving
The H-W equation is used to calculate what type of genotype frequencies?
expected
What are the 5 H-W Assumption
- Mating is random
- there are not mutations
- The population is large (no genetic drift)
- individuals do not migrate between populations (no genetic flow)
- natural selection does not occur
H-W only applies to what kind of populations?
sexually reproducing
What kind of model does H-W provide?
A useful null model
Do natural populations fit H-W?
only rarely
What does the difference between the H-W equilibrium and the observed variables mean?
how much evolutionary change is occuring in the population
In the H-W mates must be selected how?
randomly
In H-W nucleotides may or may not change due to mutations?
may not
When can genotype frequencies be determined from phenotype frequencies?
if they are assumed to be in H-W equilibrium
definition: generates genetic diversity by creating new alleles
mutation
The microevolutionary forces are what?
mutation, genetic drift, genetic flow, natural selection
What will eliminate or reduce harmful mutations?
natural selection
definition: mutations with minor effects
neutral mutations
What happens to neutral mutations?
they may persist in a population and be adaptive later as the environment changes
What would happen if a bacterium acquires a mutation that causes it to be unaffected by a particular chemical?
the mutations would become beneficial when the chemical is used later
What changed allele frequencies by creating new alleles in a populations?
mutations
mutations are essential to produce what?
genetic variation
do mutations significantly change frequencies?
do not
definition: occurs when random events cause allele frequency changes especially in smaller populations
genetic drift
What does genetic drift do to genetic variation
decreases it
what does genetic drift do to genetic differences between populations?
increases genetic differences
is genetic drift adaptive?
no it isnt
definition: genetic drift a sudden decrease in a population size caused by environmental factors
bottlenecks
What happens to the surviving population of a bottleneck genetic drift?
They have different allele frequencies compared to the original population
definition: genetic drift an event that occurs when a few individuals from a large population colonize a new area
founder event
What happens to the founding population’s allele frequencies in a founder event?
They have different allele frequencies
definition: when allele frequencies change because alleles are carried from one population to another by the migration of breeding individuals
gene flow
what does gene flow do to genetic variability of the population?
it increases genetic variability
What does gene flow do to genetic differences?
it decreases genetic differences in a population
If gene flow is extensive what could happen?
the population could become genetically similar
Is gene flow adaptive?
not necessarily
definition: changes allele frequencies by selecting the phenotypes that are more fit in current environment
natural selection
What happens to less fit phenotypes in natural selection?
they are reduced or eliminated
definition: the relative ability of a genotype to make a genetic contribution to future generations
fitness
Is natural selection adaptive?
yes that is how the alleles are chosen
natural selection can only choose from what in a population?
genetic variants; alleles that already existq
what are the types of natural selection?
stabilizing, directional, heterozygote advantage
definition: type of natural selection that selects against phenotypic extremes
stabilizing selection
What does stabilizing selection do to genetic variation?
decreases it
What individuals does stabilizing selection favor?
those with average phenotypes
definition: type of natural selection that selects for phenotypes at one extreme
directional selection
What affects directional selection?
environmental changes
definition: maintains alleles in a population that are unfavorable in the homozygous state
heterozygote advantage
which genotype has the lower fitness in heterozygote advantage?
homozygote
What does heterozygote advantage do to genetic diversity?
maintain it.
