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10 Cards in this Set
- Front
- Back
What are two primary genetic mechanisms that cause inbreeding depression? Which mechanism is thought to be the most common cause?
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1. increased homozygosity:
expression of a greater number of deleterious recessive alleles in inbred individuals, lowering their fitness 2. reduced heterozygosity: reduces the fitness of inbred individuals at loci where the heterozygotes have a selective advantage over homozygotes |
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Which of the two mechanisms that cause inbreeding depression does not allow for purging? Why is purging impossible at loci evolving under this mechanism?
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reduced heterozygosity:.
alleles with minor effects are unlikely to be purged selection cannot effectively target harmful alleles when they are spread across many different loci and different individuals |
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How is inbreeding depression measured?
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an increase in recessive deleterious alleles
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Define heterosis. Give some examples of species for which this has occurred
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● offspring are more fit than parents
○ (genetic rescue)migrants with fresh genetic material are introduced to inbred populations, ● Several examples –Adders –Prairie chickens –Drosophila –Topminnow fish –Florida panthers |
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How does inbreeding occur in large populations?
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–Selfing ( inbreeding within local populations)
–Non-random mating e.g. proximity in trees |
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How does inbreeding occur in small populations?
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–All or most individuals related
–Population of 2: after one generation, only brother-sister matings are possible *allele frequencies in individual populations will change due to genetic drift, but average frequency over a large number of replicate populations will be unchanged *One small population left, allele frequencies will change due to drift |
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inbreeding:
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•The increase in genome-wide homozygosity caused by mating between related individuals (e.g. daughter-father, cousin-cousin); non-random mating
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inbreeding depression:
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loss of fitness (survival or reproduction) as a consequence of mating among relatives
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Which mechanism for inbreeding depression is thought to be the most common cause?
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increased homozygosity
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purging
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deleterious recessive alleles may reach substantial frequencies in large random mating populations because most copies are present in heterozygotes and therefore are not affected by natural selection
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