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41 Cards in this Set

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_______ biology’s central unifying concepts. It refers to the genetic changes in populations’ gene pools over time.

evolution

__________ is a unit of evolution. It refers to all the individuals of one species that are present and interbreeding at a specific geographic location

Population

Gene Pool

-all gene copies in the population.


-size of gene pool= 2xN (N= # individuals breeding)


-can be described by genotype/ allelic frequencies

__________________ is a genetic trait w/ 2 or more distinct phenotypes.

Polymorphism

___________ are proteins from different alleles

Allozymes

What are ways of estimating genetic variation? (4)

-visible phenotypic polymorphisms


-choromosomal mutations


-protein electrophoresis


-DNA variation (sequencing)

Patterns of genetic variation can be explained by what? (5)

-mate choice


-mutation


-dispersal (migration/ gene flow)


-natural selection


-genetic drift

The hardy-weinberg principle consists of (3)...

-diploid, sexually reproducing species. It is assumed that every individual makes an infinite # of gametes


-Gametes are randomly mixed in a “gamete pool”.


-Gametes are randomly picked to form zygotes that represents the next generations, however, all adults die (Non-overlapping generations)

H-W Model Assumptions- HW equilibrium is ONLY found with (5)...

-random mating


-large population size (no genetic drift)


-no mutation


-no migration


-no natural selection

How can you tell if a gene pool have H-W fre quencies?

-Compare the expected genotype frequencies to observed w/ a chi-square goodness-of-fit test


-If null hypothesis is rejected, the population doesn’t have H-W genotype frequencies. One of the 5 forces must be acting.

Matings based on phenotype/ genetic relatedenss

Phenotype:


-Positive Assortative Mating- mate w/ same phenotype more often (HoHe))negative>

-Negative Assortative Mating- mate w/ same phenotype less often (Ho>He)
)negative>


)negative>


Genetic Relatedness:)negative>


-Outbreeding- mate w/ relatives less often (affects all genes; Ho>He))negative>


-Inbreeding- mate w/ relatives more often (affects all genes; Ho



)negative>

Inbreeding Depression

because inbreeding leads to increase chances of rare alleles being presented, then it leads to a decrease in survival/ reproduction

T/F: Mutation occurs at a higher rate than migration.

False; Mutation is slow!

T/F: With the forward-backward mutation model, you will eventually reach equilibrium, despite which allele frequency you start off w/ (equilibrium= no net change of allele frequency; fixated).

True!

Migration and Gene flow both bring in new alleles into a population. Their rates are much


_______ than mutation rates.

higher

What is known as the great homogenizer?

Gene flow- alters freq. within populations, but reduces genetic dif. among populations

Is speciation retarted from gene flow? why?

yes, because it requires genetic divergence (ability to be separated). genetic isolation is required to eliminate homogenizing effect of gene flow (need a barrier to prevent species from migrating into each other’s population).

One-Way Migration

-example of this is wind blowing in one direction. Individuals from population 1 (due to factors such as wind) migrate into population 2.


-After migration, allele frequencies in the source (population 1) are constant, while population 2 consists of proportion of ‘m’ migrants and ‘1-m’ of residents.


-Eventually at equilibrium, the destination will reach the same as the source

Island Model Migration (migration is two-way) Assumptions.... (4)

-ALL populations are discrete “islands” (no mainland)


-ALL populations are equal in size, migration rate… but p and q don’t have to be the same in each population


-The number of populations is large


-Migration among “islands” is not distant dependent (migration rate m is constant over populations/ time)

__________ is due to random sampling error of gametes.

Genetic Drift

______________ is the probability of a random event is only a theoretical expectation. Observed outcomes may differ from expected outcome; this has a larger impact on smaller populations.

Random Sampling Error




EX) flip a coin 10 times: you expect to get 5 heads/ 5 tails, but if you get 6 heads, then that’s a 20% deviation due to RSE. However, if you flip 1000 times, a 20% deviation (600 H/ 400 T) is very unlikely.

T/F: Fertilization is not subject to random sampling error

False; it is



there are finite number of zygotes, which leads to RSE in gamete allele frequencies


T/F: Genetic Drift causes allele frequencies within a population to change over time (e.g. reach fixation)

True!

T/F: THere is more GD in larger populations

False; there is less GD in larger populations

Genetic drift causes population to ________ over time.

Diverge

Effective Population Size

-number of individuals able to breed

Genetic Drift causes ______ alleles to be lost easily. W/o variation, population eventually becomes __________.

rare alleles; monomorphic

T/F: Genetic drift depends on Effective Population Size, not the actual # of individuals.

True!

T/F: Genetic variation is lost slower when Effective Population Size is smaller

False; lost faster

Bottleneck Effect

reduction in population due to subpopulation being separated (i.e. form volcanoes, earthquakes, landslides etc.). A case of genetic drift.

Founder Effect

new pop. initiated by small numbers of “founders”. Founders are only a SAMPLE of the source population. They are proned to Genet Drift, and lose variation. A case of genetic drift.

Natural Selection

-increase in the freq of beneficial alleles over time due to inc survival and reproductive success of ind. carrying those alleles


-Other Forces Involved: Even if NS selects for/ against an allele, other ev. forces will impact the selection of that allele.

T/F: Natural selection operate on genotypes, causing populations to better ADAPt to their environment.

False; operates on phenotypes

_______________ refers to the capacity to survive/ reproduce based on phenotypic dif. among ind.

Fitness

What are the 4 different types of selection?

-Gametic Selection- some genes in gametes more compatible than others


-Viability Selection- avg. % survival


-Sexual Selection- mating


-Fertility Selection- avg. # offspring per surviving adult

What are the 4 types of natural selection?

-complete dominance- selection against recessive allele


-partial dominance


-overdominance- selection against homozyogote


-underdominance- selection against heterozygote

complete domoninance

-selection against recessive allele

-A2 can be fixed if there were no A1 alleles initially


-The rate of fixation of the recessive alleles decrease after each generation because the rec. found most freq. in heterozygotes

Partial Dominance

for s>0 and p>0, population becomes fixed for A1 (stable)for p=0, population remains fixed for A2 (unstable)

Underdominance

- selection against heterozygote/ heterozygotes have lowest fitness


-population becomes fixed for A1 or A2= stable equilibrium. But if both alleles exist in the population, there’s unstable equilibrium.


-If p=.5 & q=.5, then i’s unstable equilibrium

Overdominance

-selection against both homozygotes (S11/ S22 don’t have to be the same)


-Two unstable equilibrium (fixed for A1 or A2)


-THE ONLY NS THAT MAINTAINS POLYMORPHISM/ THE MOST DIVERSITY!


-rare in nature/ not plausible

What's the only natural selection that maintains polymorphism?

overdominance- against homozygotes