Unit 3 * Evolution Lesson 1 * Mutations and Artificial Selection

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What is evolution and why is it important?
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The mechanism that drives evolution is
natural selection.
Natural Selection: the way in which nature
favours the reproductive success of some
individuals within a population over others.
Genetic diversity must be present for nature
to favour some individuals over other
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Mutations are the source of genetic variation
What mechanisms have we studied that
increases this genetic diversity?
Substitution
A substitution is a mutation that exchanges one
base for another (i.e., a change in a single
"chemical letter" such as switching an A to a G).
-Such a substitution could cause a small change in
the protein produced.
For example,sickle cell anemia is caused by a
substitution in the beta-hemoglobin gene, which
alters a single amino acid in the protein
produced.
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Heritable disease
Codominant
Chronic pain caused
by RBCs moving
through blood
vessels.
Stroke, other
cardiovascular
complications
Insertion
Insertions are mutations in which extra base
pairs are inserted into a new place in the
DNA.
Deletion
Deletions are mutations in which a section of
DNA is lost, or deleted.
Neutral mutation - a mutation that does not
result in any selective advantage
or disadvantage.
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Harmful mutation - any mutation that reduces
the reproductive success of an individual and is
therefore selected against; harmful mutations
do not accumulate over time
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Beneficial mutations - are favoured by natural
selection and accumulate over time
Artificial selection - directed breeding in which
individuals that exhibit a particular trait are
chosen as parents of the next generation;
artificial selection is used to produce new
breeds or varieties of plants and animals
1. Choose a useful species that can be bred in
captivity.
2. Breed a large number of individuals.
3. Choose a trait that you wish to favour, such as
large size, a particular colour, or sweetness.
4. Identify individuals that exhibit the favoured
trait most strongly.
5. Breed only these individuals to produce the next
generation of individuals.
6. Repeat Steps 4 and 5 over many generations.
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Artificial Selection is limited by the genes that
are present in the current population.
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