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Lecture

Readings 6 notes


Department
Biological Sciences
Course Code
BIOC51H3
Professor
Maydianne Andrade

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Readings 6
Pgs210 -218 (refer to example on pgs.210-211 and 211-214)
-cystic fibrosis is inherited as an autosomal recessive trait
-new disease alleles are constantly introduced into populations by mutation
-mutation by itself is generally not a rapid mechanism of evolution
-back mutations that restore function are much less common than loss of function mutations
-back mutations convert loss of function copies a into wild type A
-mutation converts 1 of every 10 000 copies of an allele A into a new copy of allele a
-mutation can cause substantial change but it does so slowly (it can add and remove alleles)
-in combination with selection, mutation becomes a crucial piece of the evolutionary process
-within any given population, fitness increases dramatically in response to natural selection
-each new mutation that benefits a population becomes fixed over time
-selection acts to eliminate such mutations from populations because they are deleterious
-deleterious alleles persist because they are continually created anew
-mutation t selection balance is the equilibrium of an allele frequency when the rate of
deleterious mutations eliminated is equal to their rate of creation
-the equilibrium frequency of a recessive allele at equilibrium is
AOR/ s where µ is the mutation rate and s is the selection coefficient between 0 and 1
-if selection coefficient is small and mutation rate is high, then equilibrium of the allele
frequency will be high
-disease alleles are kept in the population by a balance between mutation and selection
-cystic fibrosis transmembrane conductance regulator (CFTCR) has the function of enabling cells
of the lung lining to inject and destroy bacteria
-cystic fibrosis is caused by chronic lung infections from bacteria
-cystic fibrosis disease alleles are maintained in human populations because heterozygotes
have superior fitness during typhoid fever epidemics (heterozygote superiority)
-the effect of mutation can cause a change in allele frequency using the equation
p* = p - µp where p* is the new allele frequency for A, µ is the mutation rate, and p is the
original allele frequency for A
q* = q + µp where q* is the new allele frequency for a and q is the original allele frequency for a
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