Unit 3 – EvolutionLesson 1 – Mutations and Artificial Selection

Unit 3 – Evolution

Evolution

What is evolution and why is it important?

Genetic Diversity and Evolution 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

Mutations and Genetic Diversity Mutations are the source of genetic

variation What mechanisms have we studied

that increases this genetic diversity?

How Mutations Occur

SubstitutionA 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.

Sickle Cell Anemia

Heritable disease Codominant Chronic pain

caused by RBCs moving through blood vessels.

Stroke, other cardiovascular complications

How Mutations Occur

InsertionInsertions are mutations in which extra base pairs are inserted into a new place in the DNA.

DeletionDeletions are mutations in which a section of DNA is lost, or deleted.

Types of Mutations Neutral mutation - a mutation that does not

result in any selective advantageor disadvantage.

Harmful mutation - any mutation that reduces the reproductive success of an individual and is therefore selected against; harmful mutations do not accumulate over time

  Beneficial mutations - are favoured by

natural selection and accumulate over time

Articifical Selection

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

Guide to Artificial Selection1. 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.

Limitations of Artificial Selection Artificial Selection is limited by the

genes that are present in the current population.

Induced Mutations

Thalidomide