Download Evolution Hardy-Weinberg Equilibrium Model

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
p2 + 2pq + q2 = 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
2
(p + q) 2 = 1
p2 + 2pq + q2
p2 = AA
2pq = Aa
q2 = aa
Albinism
Homozygous
recessive (aa)
1/20,000
q2 = 1/20,000 =
.00005
q = .007
p=1-q
p = 1 - .007
p = .993
p2 + 2pq + q2 = 1
(.993) 2 + 2 (.993)(.007) + (.007) 2 = 1
.98605 + .01399 + .00005 = 1
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Further Calculations
p2 = (AA) = .98605 = 98.6%
2pq = (Aa) = .01399 = 1.4%
q2 = (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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