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10/14 Daily Catalyst Pg. 33 Variation
 1. If 1/350 people have blue eyes, what frequency of the
population is hybrid for brown eyes? Homozygous for
brown eyes?
 2. How does sexual reproduction produce variation?
 3. Why are point/substitution mutations also known as
silent mutations?
10/14 Daily Catalyst Pg. 33 Variation
 1. If 1/350 people have blue eyes, what frequency of the population
is hybrid for brown eyes? Homozygous for brown eyes?
 2. How does sexual reproduction produce variation?
 A population contains a vast number of gene combinations. Sexual
reproduction reshuffles alleles into fresh combinations.
 3. Why are point/substitution mutations also known as silent
mutations?
 These mutations may not change the amino acid and the protein so
the mutation have not effect!
10/14 Class Business Pg. 33 Variation
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John Ehret Patriots Bring the `Pain Spirit Day Extra Credit
Quiz #7:
Average: 1.72
Top Score: Travia, 3.7
10/14 Agenda Pg. 33 Variation
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Daily Catalyst
Class Business
Hardy-Weinberg problem
Variation notes
Debate Prep
Homework: 137-142
Hardy Weinberg Equilibrium
 There are 100 students in a class. Ninety-six did well in the course
whereas four blew it totally and received a grade of F. Sorry. In
the highly unlikely event that these traits are genetic rather than
environmental, if these traits involve dominant and recessive
alleles, and if the four (4%) represent the frequency of the
homozygous recessive condition, please calculate the following:
 A. The frequency of the recessive allele.
 B. The frequency of the dominant allele.
 C. The frequency of heterozygous individuals.
Essay Prompt
 Of all the mutations that occur, why do only a small fraction
become widespread in a gene pool?
 Most mutations occur in somatic cells that do not produce
gametes and are lost when the organisms die. Of the mutations
that occur in the gametes, most do not have an effect on
phenotypes and natural selection will not act on it. If you do have
a harmful mutation, most will not survive to reproduce.
Causes of Evolution
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1. Mutations
2. Sexual Recombination
3. Genetic Drift
4. Genetic Flow
5. Natural Selection
Genetic Drift:
 Unpredictable changes in allele frequencies from one
generations because of a populations finite size
 Reduces genetic variation
Bottleneck Drift
 A reduction of a population, typically after a
disturbance, such that the survivors no longer
represent the original population
 Example?
Founder Effect
 A small isolated group that may establish a new
population.
 Represent a distinct gene pool from the parent gene
pool
 Example?? (page 462)
Gene Flow:
 Genetic additions and/or
subtractions from a
population resulting from
the movement of
individuals.
 How has this been
important to humans?
Genetic Variation
 Key Point #1:
 Natural Selection accumulates and maintains favorable
genotypes in a population.
 WE NEED GENETIC VARIATION!
Variation in Variation (get it??)
Examples of variation
 Key Point #2:
 Polymorphism: Two or more distinct morphs
represented in high amounts
 Morphs: different forms of a characteristic
Examples of Variation
 Kordell mentioned yesterday, that he has noticed that
in different geographical locations, he has seen traits
that are more common in areas and not as common in
other.
Examples of Variation
 Key Point #3:
 Geographic variation:
 Differences between gene pools of separate populations
 Cline: page 464
Natural Selection
 Directional (pg. 465)
 Stabilizing (pg. 466)
 Disruptive (pg. 466)
Directional Selection
Stabilizing Selection
Disruptive Selection
Heterozygote Advantage:
 Pg. 466