Evolution

Environmental factors causing variation

Diseases, radiation

Genetic factors causing variation (main cause of variation)

• sexual reproduction

• chromosomal abnormality

• mutation

Aneuploidy chromosomal abnormality

Extra or missing chromosomes

Polyploidy chromosomal abnormality

All chromosomes replicated

Block mutation (chromosomal)

• Addition/duplication

• Deletion

• Translocation

• Inversion

Substitution mutations: silent (point)

Substituted base, same amino acid

Substitution mutations: missense

Substituted base, different amino acid

Different protein function and cascade effect

Substitution mutations: nonsense

Substituted base creates stop codon

Protein is short and non-functional

Mutation: frame shift

Addition/deletion of base

Altered reading frame as amino acids read in groups of 3 bases.

Gene flow

Movement of variation through a population

Gene drift

Change in allele frequency

Gene drift - Bottleneck

Random of removal of genetic variation. Reduction in population size, resulting in limited variation (selective pressure) which results in extinction.

Gene drift - founder effect

Movement of a small founding population to an isolated location. Lack of gene flow promotes increase in allele frequency of normally recessive traits.

Natural selection process

1. Variation in the population

2. Selective pressure

3. One variant will be “selected for”