Evolution change in frequencies of alleles in the gene pool; e.g., Allele frequencies in parents: B = .92 and b = .08; in their offspring B= .90 and b = .10
Charles Darwin
British Naturalist
1809 -1882
I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.
Hardy-Weinberg Equilibrium
Model & The Paradox
Through mathematical modeling, they concluded that gene pool frequencies are inherently stable but that evolution should be expected in all populations virtually all of the time.
Five Conditions
No mutation
No natural selection
Population is infinitely large
All mating is random
No migration
[All members breed and everyone produces equal numbers of offspring]
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Mechanisms of Evolution
Mutation
Natural selection
Genetic drift
Non-random mating
Migration
”I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.” (Darwin)
Hardy-Weinberg Equilibrium
Equation p 2 + 2pq + q 2 = 1 p = frequency of dominant allele q = frequency of recessive allele
Another way to collocate allele frequencies p = AA + 1/2 Aa q = aa + 1/2Aa p + q = 1 p = 1 – q q = 1- p
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(p + q) 2 = 1 p 2 + 2pq + q 2 p 2 = AA
q 2 = aa
Albinism
Homozygous recessive (aa)
1/20,000 q 2 = 1/20,000 =
.00005
q = .007
p = 1 q p = 1 .007 p = .993 p 2 + 2pq + q 2 = 1
(.993) 2 + 2 (.993)(.007) + (.007)
.98605 + .01399 + .00005 = 1
2 = 1
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Further Calculations p 2 = (AA) = .98605 = 98.6%
2pq = (Aa) = .01399 = 1.4% q 2 = (aa) = .00005 = .005% (the albinos)
PTC Taste Testing
Phenylthiocarbamide
Phenylthiourea
Tasters: TT or Tt
Non-taters = tt
Evolutionary Implications thyroid disease non-tasters more prevalent among hypothyroid patients non-tasters more susceptible to nonendemic nodular goitre tasters have a lower incidence of dental caries
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