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transposition
the production of copies that become inserted into new positions in the genome
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Kinds of mutations
- Gene mutations (bp substitutions, point mutations, transition, transversion, frameshift mutations)
- Recombination
- Transposable elements --> cause changes
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synonymous mutations vs. nonsynonymous
- synonymous: no efect on amino acid sequence of the protein (often in coding region)
- Nonsynonymous: result in amino acid substitutions
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Intragenic Recombination
when homologous DNA sequences differ at two or more ase pairs -- generates new gene combinations
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recurrent mutation
repeated origin of a particular mutation
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back mutation
mutation of a mutant allele back to the allele from which it arose (usually WT)
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polygenic
the variation in most phenotypic characters is this
based on several or many different genetic loci
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homeotic mutations
redirect the development of one body segment into another (regulation of gene expression!)
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additive inheritance
if heterozygotes phenotype is precisely intermediate between the homozygotes
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pleiotropic mutations
affect more than one character
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karyotype
description of its complement of chromosomes (number, size, shape, and internal arrangement)
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aneuploid
unbalanced chromosome complement (often inviable or fails to develop properly)
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polyploidy
changes in teh number of whole sets of chromosomes (more than 2 entire sets of homologous chromosomes)
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autopolyploids
arisen by the union of unreduced gametes of the same species
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allopolyploids
arisen by hybridization between closely related species
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inversion
rearranged gene order from a loop and cross over
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pericentric vs paracentric
- pericentric = inversion that includes centromere
- paracentric = inversion that does not include centromere
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reciprocal translocation
two nonhomologous chromosomes may exchange sengemnts by breakage and reunion
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acrocentric vs. metacentric chromosomes
- acrocentric = centromere near one end
- metacentric = centromere in middle
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fusion of chromosomes
two nonhomologous acrocentric chromosomes undergo reciprocal translocation that they are joined into a metacentric chromosome
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fission of chromosomes
metacentric with acentric??? pg. 211
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environmental variance
environmentally induced variation among individuals
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maternal effect
effects of a mother on her offspring not from the gnes but to nongenetic influences (yolk in egg, maternal care, physiological condition of berthing)
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epigenetic inhereitance
when phenotypic differences not based on DNA sequence differences are transmitted among generations of dividing cells in multicellular organisms and also sometiems from parents to offspring (like DNA methylation)
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norm of reaction
variety of different phenotypic states that can be produced by a single genotype under different environmental conditions
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common garden
offspring of phenotypically different parents can be reared together in a uniform environment
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Hardy Weingburg Equillibrium assumptions
- 1. mating is random (panmictic)
- 2. population is infinitely large (no genetic drift)
- 3. genes are not added from outside the population (no gene flow)
- 4. genes do not mutate from one allele state to another (no mutation)
- 5. all individuals have equal probabilities of survival and of reproduction
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gene glow
mating among different populations (migration)
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polymorphism
presence in a population of two or more variants (alleles or haplotypes)
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monomorphic
locus/character that is not polymorphic
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inbreeding depression
- inbreeding increases the proportion of homozygotes - mroe likely to get homozygote recessive (bad)
- Therefore, decline in components of fitness (survival, fecundity)
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linkage disequilibrium
association/correlation between specific allels at two loci
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linkage equilibrium
no such association between specific alleles at the two loci
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quantitative variation
continous/metric varaition - fits a normal distribution
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polygenic
due to variation in phenotype
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sympatric vs. parapatric vs. allopatric
- sympatric = if distinct populations have overlapping geogrphic dddistributions so that they occupy the same area and frequently encounter each other
- parapatric = populations with adjacent but nonoverlapping ranges that come into contact
- allopatric = populations with spearated distributions
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Bergmann's Rule
body size increases iwth increasing latitude
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cline
gradual change in a character or in allele frequencies over geogrpahic distance
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ecotypes
phenotypes that are associated with a particular habitat, often in a partchy mosaic pattern
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random walk
random fluctuation of alleles - p will eventually wander (drift) to either 0 or to 1 (no stabilizing force)
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hitchhiking
a genotype would increase rapidly in frequency because of linkage to an advantageous mutation that had ocurred at another locus
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preadaptation
feature that fortuitously serves a new function
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exaptations
preadaptations that have been co-opted to serve a new function
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overdominant
when the heterozygote is said to be dominant
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underdominant
if heterozygote has lowest fitness
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Stabilizing selection
intermediate phenotype is fittest
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directional selection
if one extreme phenotype is fittest
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diversifying (disruptive) selection
if two or more phenotypes are fitter than the intermediates
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coefficient of slection
(s) the amount by which teh fitness of a genotype differes from teh reference genotype (1-w)
- intensity of selection agaisnt the less fit genotype
- selective advantage of the fitter genotype
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balancing selection
selection that maintains polymorphism
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factors responsible for variation
- 1. recurrent mutation producing deleterious alleles subject to weak selection
- 2. gene flow of locally deleterious alleles from other populations in which they are favored by selection
- 3. seletively neutrality (genetic ddrift)
- 4. maintenance of polymorphism by natural slection
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antagonistic selection
opposing forces acting on polymorphisms - usually does not maintain polymorphisms
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inverse frequency dependent selection
the rarer a phenotype is in teh population the greater its fitness
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positive frequency dependent selection
- the fitness of a genotype is greater the more frequent it is in the population
- whichever allele is initally more frequent will be fixed
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selective sweep
reduction/elimination of DNA sequence variation in teh vicinity of a mutation that has been fixed by natural selection relatively recently
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