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41 Cards in this Set

  • Front
  • Back
population genetics
study of genetic variablilty within a population & of the forces that act on it
gene pool
includes all the alleles for all the loci present in the population.
genotype frequency
proportion of a particular phenotype in the population. expressed as a decimal. (if 49% of a population has blue eyes, the genotype frequency is .49)
phenotype frequency
proportion of a phenotype
allele frequency
proportion of a specific allele.
genetic equilibrium
frequencies of alleles and genotypes don't change from generation to generation unless influenced by outside forces
evolution
allele frequencies change over succesive generations
Hardy-weinberg equilibrium
refers to an "ideal population" (perfect, where no evolution is occuring)
p=
q=
p + q= ?
frequency of a dominant allele
frequency of a recessiv allele
1.0
p2
q2
2pq
frquncy of AA
frquency of aa
frquency of Aa
Genetic equilibrium
if 5 conditions are met:
1- random mating
2- no net mutations
3- large population size
4- no migration
5- no natural selection
random mating
each individual has an equal chance of mating with any individual of the opposite sex
no net mutations
no mutations to convert alleles.
large population size
allele frequencies in a large population won't be changed by random fluctuations
no migration
no exchange with other populations that might have difrent allele frequencies. no individuals going in or out
no natural selection
if certain phenotypes are favored, the allele frequency will chage and evolution will occur
microevolution
evolution within a population
2 examples of nonrandom mating
inbreeding & assortative mating
inbreeding
mating of genetically similar individuals that are more related than if they were chosen at random from the entire population
self-fertilization
an example of inbreeding.
inbreeding depression
inbred individuals have lower fitness
fitness
relative ability of a given genotype to make a genetic contriution to subsequent generations

measured by the # of offspring who survive and pass on their genes to their offspring
homozygosity
mortality caused by expression of recessive alleles
assortative mating
individuals select their mates by attraction.(nonrandom mating)
mutation
unpredictable, spontaneous. mutations in somatic cells don't get passed down.
genetic variability
increases by mutations.
genetic drift
production of random evolutionary changes in small breeding populations. alleles may be eliminated by chance
genetic bottleneck effect
fluctuations in the environment-depletion of food, disease, hurricanes- population may rapidly decrease from time to time
founder effect
when one or a few individuals from a large population find a new colony
gene flow
migration of indivuals causes a movement of alleles
sufficient gene flow
populations become more similar genetically
natural selection
differential reproducitve success. weeds out those individuals whose phenotypes are less adapted
stabilizing selection
phenotypic extremes are selected against.
ex: human birth weight-7 lbs
directional selection
if environment changes...directional selection may favor phenotypes at one of the extremes
disruptive selection
evironment favors 2 or more diffrent phenotypes.
what makes genetic variation?
-crossing over
-independent assortment of chromosomes
-union of gametes
genetic polymorphism
presence in a population of 2 or more genes for a given locus
balanced polymorphism
2 or more alleles persist in a population over many generations b/c of natural selection
heterozygote advantage
heterozygote has a higher degree of fitness.
sickle-cell anemia and heterozygote
Aa-normal
AA- die of malaria
aa- die of sickle cell
neutral variation
variation that does not alter the ability of an individual to survive and reproduce and not adaptive