Download Genetic Mutations

Unit 11
Evolution
114
Population Evolution
Notes
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115
EQ:
Genetic Mutation
Summary
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Slide 1 of 3
Genetic Mutations
EQ: How does genetic mutation affect evolution?
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The two main sources of
genetic variation are
mutations and gene shuffling.
 A mutation is any change in
a sequence of DNA.
(CGA to GGA, then the codon
changes)
Gene shuffling occurs during
the production of gametes in
sexual reproduction.

(Chromosomes crossing-over
during meiosis)
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Slide 2 of 3
Genetic Mutations
Genetic mutation continually produces variations
among individuals with a species.
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Without a constant supply of mutations evolution
would stop
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Genetic Mutations
A mutation could cause parents with genes for
bright green coloration to have offspring with a
gene for brown coloration. That would make the
genes for brown beetles more frequent in the
population.
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Genetic Mutations
To understand evolution, genetic variation is studied in
populations.
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• A population is defined as a group of individuals of
the same species that interbreed.
• Members of a population share a common group of
genes, called a gene pool.
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• A gene pool consists of all the genes, including all
the different alleles, that are present in the
population.
• The relative frequency of an allele is the # of times
that allele occurs in a gene pool, compared with the
# of times other genes occur.
Summary
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Natural selection acts on individuals.
Evolution acts on populations.
Natural selection acting on individuals,
leads to the evolution of populations.
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Slide 1 of 4
Population Evolution
Migration also contributes to
genetic variation
Individuals immigrating into a
population bring new alleles with
them. This causes a change in allele
frequencies in a population.
Read:
Some individuals from a population
of brown beetles might have joined
a population of green beetles.
That would make the genes for
brown beetles more frequent in the
green beetle population.
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Slide 2 of 4
Population Evolution
Genetic Drift: random change in
allele frequency. In small
populations, alleles can become
more or less common simply by
chance.
Read:
Imagine that in one generation,
two brown beetles happened to
have four offspring survive to
reproduce. Several green beetles
were killed when someone stepped
on them. The next generation
would have a few more brown
beetles than the previous
generation — but just by chance.
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Population Evolution
\
The Bottleneck Effectnonselective
population reductions
due to disasters.
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Population Evolution
The Founder Effect -The
colonization of a new habitat
by a small group (founders) of
individuals -due to migration.
The genes (alleles) of the
founder community are
disproportional to the rest of
the population.
An real example of the founder effect:
The Amish community has a high concentration of individuals with
Polydactyly because they have isolated themselves.
They are the “founders”.