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Definition
| when only one dominant and one recessive allele exist for a given gene |
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| when more than one dominant allele exists for a given gene |
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| when a heterozygote expresses a phenotype that is intermediate between the two homozygous gentoypes |
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| a population measure defined as the proportion of individuals in the population carrying the allele who actually express the phenotype; full penetrance means 100% of people with the allele display the phenotype, nonpenetrance would be no indivduals with the allele show the phenotype |
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Definition
varying phenotypes despite identical genotypes
- constant expressivity - all individuals with a given genotype express the same phenotype
- variable expressivity - inviduals with the same genotype may have different phenotypes
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Definition
| all of the alleles in a given population |
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| elements that can insert and remove themselves from the genome |
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Definition
| large scale mutations affecting whole segments of DNA |
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| when a segment of DNA is copied multiple times |
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| when a segment of DNA is reversed |
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| when a segment of DNA is moved from one chromosome to another |
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Definition
| when a segment of DNA is swapped with a segment of DNA from another chromosome |
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| a flow of genes between species through hybrid offspring |
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Definition
| occurs when the composition of the gene pool changes as a result of chance; more pronounced in small populations |
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| more extreme case of genetic drift in which a small population of a species finds itself in reproductive isolation from other populations |
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Definition
| events that suddenly isolate a small population |
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| loss of genetic variation causing a reduced fitness of a population |
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Term
| outbreeding or outcrossing |
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Definition
| introduction of unrelated individuals into a breeding group |
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Definition
| the organism with an unkown genotype is crossed with an organism known to be homozygous recessive |
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Definition
| the likelihood of two alleles being separated during corssing over in meiosis; a 0% percent recombination frequency means they never recombine and are very strongly linked |
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Definition
| how often an allele appears in a population |
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Definition
if the below criteria are met, then the allele frequencies will remain constant
- the population is very large
- there are no mutations that affect the gene pool
- mating between individuals in the population is random (no sexual selection)
- there is no migration of individuals into or out of the population
- the genes in the population are all equally successful at reproducing
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Term
| Hardy-Weinberg equilibrium equations |
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Definition
where p and q are the frequency of two alleles, adding them together must equal 1 because they are the only two choices
square both sides of the equation
p2 is the frequency of one homozygous genotype and q2 is the other. pq represents the heterozygous genotype. If the frequencies of these alleles stays the same from generation to generation a population is at Hardy-Weinberg equilibrium
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Term
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Definition
| considers an organism's success to be based on the number of offspring, success in supporting offspring, and the ability of the offspring to then support others; survival of offspring or relatives ensures continuation of genes in subsequent generations |
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| considers evolution to be a very slow process with intermittent rapid bursts of evolutionary activity |
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| keeps phenotypes in a narrow range, excluding extremes |
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| moves the average pehnotype toward one extreme |
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| moves toward two different phenotypes at the extremes and can lead to speciation |
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| the rapid emergence of multiple species from a common ancestor, each of which occupies it own ecological niche decreasing competition for resources |
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| the largest group of organisms capable of breeding to form fertile offspring |
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| the formation of a new species through evolution |
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| when progeny of two populations can no longer freely interbreed |
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| prezygotic mechanisms vs postzygotic mechanisms |
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Definition
- prevent formation of the zygote completely
- allow for gamete fusion but yield either nonviable or sterile offspring
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| occurs when two species sharing a common ancestor become more different |
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| occurs when two species sharing a common ancestor evolve in similar ways due to analogous selection pressures |
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Definition
| occurs when two species not sharing a recent ancestor evolve to become more similar due to analogous selection pressures |
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| the degree of difference in the genome between two species is related to the amount of time since the two species broke off from a common ancestor |
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