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Lecture 12

BIOL 1F90 Lecture 12: BIOL 1F90 lecture 12 winter 2016

Biological Sciences
Course Code
Fiona Hunter

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Friday, January 29, 2016
Lecture 12
Bottleneck E!ect
-population reduced dramatically and then rebuilds
-randomly eliminated members without regard to genotype
-surviving members may have allele frequency dierent from original population
-now population likely to have less genetic variation
Founder E!ect
-small group of individuals separates from a larger population and establishes a new colony
-relatively small founding population expected to have less genetic variation than original
-allele frequency in founding population may dier markedly from original population
Neutral Theory of Evolution
-non-Darwinian evolution
-neutral variation
-much of variation seen in natural population ins caused by genetic drift
-doesnt preferentially select certain traits
-most genetic variation is due to the accumulation of neutral mutations that have attained
high frequencies due to genetic drift
-neutral mutations do not aect the phenotype so they are not acted upon by natural
-main idea is that much of modern variation in gene sequence is explained by neutral
variation rather than adaptive variation
-sequencing data supports this idea
-nucleotide substitutions much more likely in third base of codon (usually doesn’t change
amino acid) than first or second (usually does change amino acid)
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