L41 BIOL 2970 Lecture 28: Bio 12-05
6 Feb 2019
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Department
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Bio 12-05
Isolation by Distance-Sewall Wright (Fst)
-Fst is a way of asking the question how much diversity exist between different groups of a
population as opposed to differences among individuals within individuals
-the higher the fst the more distinct local populations are genetically
-we’ve used Fst as a pairwise distance measure- we can use neighbor-joining method
(distance matrix method) to construct a tree
-partial isolation only
-most gene flow is between neighboring demes, with genetic differences among populations
being proportional to their geographic distances
-pattern of gene flow across geographic space occurs primarily within a deme and
between neighboring demes
-few cases of an individual traveling large distances before mating
-a new mutation can spread throughout the entire species even if no individuals move long
distances
-each local demes is a “stepping stone” and genes can take many generations to cross
such stepping stones
-mutation in france could still reach eastern china as long as demes are connected by
intermediate demes but it would take many generations
-best predictor of genetic differentiation among human population is geographic distance
Haplotype Trees-used to measure genetic structures of populations
-Haplotypes have geographic distributions.
-Isolation by distance- younger haplotypes have smaller geographic distributions located within
the ranges of their ancestral haplotypes.
-Geographic range expansion- a population undergoes long distance expansion into previously
uninhabited areas
-younger haplotypes can have geographic distributions well outside the ranges of the
ancestral haplotype
Document Summary
Pattern of gene flow across geographic space occurs primarily within a deme and. Few cases of an individual traveling large distances before mating. The higher the fst the more distinct local populations are genetically. We"ve used fst as a pairwise distance measure- we can use neighbor-joining method. Fst is a way of asking the question how much diversity exist between different groups of a population as opposed to differences among individuals within individuals (distance matrix method) to construct a tree. Most gene flow is between neighboring demes, with genetic differences among populations being proportional to their geographic distances between neighboring demes. A new mutation can spread throughout the entire species even if no individuals move long distances such stepping stones intermediate demes but it would take many generations. Best predictor of genetic differentiation among human population is geographic distance. Haplotype trees-used to measure genetic structures of populations.
