Evolution- Genetic drift

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  • Created by: Sarah
  • Created on: 22-04-13 16:55
How can genetic drift be a cause of non-adaptive evolution?
Leads to replacement of old alleles by new alleles and all loci/alleles are subject to genetic drift. This is why it is the null hyp for explaining change!
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What is genetic drift as sampling error?
Random changes in gene frequencies between genes, independent of selection...etc
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Fixation is never reached in populations, T or F?
F- if left long enough all pops will reach fixation eventually.
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Sampling error causes allele frequencies to wander between 0 and 1 in what sort of population?
Finite pop with no selection, mutation or migration
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What affects an alleles probability of being fixated?
Its initial frequency in the pop x/2N
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What happens when alleles drift towards fixation?
Heterozygosity
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Loss of heterozygosity occurs more frequently when....?
In small pops as alleles are fixed more rapidly
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The frequency of heterozygotes is always a) more b) less in the next gen?
Less
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If N (Number of indivs in pop) is large the decrease in H is a) small b) large
Small
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What is bottlenecking?
A rapid decrease in pop size usually results in loss of rare alleles and loss of heterozygosity
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In founder effect, the level of H is not reduced much in the first gen, T or F?
T
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In the frequency of heterozygosity relationship, the value is always between what?
1/2 when N=1 and 1 when N= infinite
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Why is speed of pop growth important in loss of heterozygosity?
Limits how quickly the pop recovers after a bottleneck
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What is the effective pop size (Ne)?
The size of an ideal theoretical pop that would lose heterozygosity at the same rate as the actual pop (number of individuals in pop who actually breed)
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What are the 4 factors which influence Ne?
variation in progeny number (If some have more offspring than others Ne will reduce), overlap of generations (incest causes Ne genes to reduce), unequal number of males & females, fluctuations in pop size (genetic drift increases in small pops)
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What are the effects of genetic drift?
small pops diverge faster than big ones, loss of heterozygosity and genetic diversity,
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The inbreeding coefficient increases more rapidly in...
small pops than bigger pops
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What are the 3 aspects of inbreeding depression?
reduces heterozygosity, exposes rare deleterious recessive alleles, loss of genetic diversity
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Other cards in this set

Card 2

Front

What is genetic drift as sampling error?

Back

Random changes in gene frequencies between genes, independent of selection...etc

Card 3

Front

Fixation is never reached in populations, T or F?

Back

Preview of the front of card 3

Card 4

Front

Sampling error causes allele frequencies to wander between 0 and 1 in what sort of population?

Back

Preview of the front of card 4

Card 5

Front

What affects an alleles probability of being fixated?

Back

Preview of the front of card 5
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