Mutation, Genetic variation and Evolution

What are mutations

Inherited alterations in genetic material

Germ line mutations

occur in gametes and are inherited (rare)

Somatic mutations

Mutations that occur in body cells, aren't passed to offspring, and don't affect the gametes (common)

Substitution mutation

A single codon is affected so doesn't have an effect

Insertion mutation

inserts random base - effects the reading frame and change many codons

Deletion mutation

removes base - effects the reading frame and change many codons

missense, nonsense, silent

3 types of point mutations

missense - is change in amino acid sequence

nonsense - new codon is a stop codon so premature termination of translation

silent - new codon codes the same amino acid no change

What mutation occurs in people with cystic fibrosis?

in-frame deletion of three nucleotides

Frame shifts

caused by insertions and deletions

Forward mutation

changes the wild type into a mutant phenotype

Reverse mutation

restores the wild type gene and the phenotype

Suppressor mutation

occurs at a site different from that of the original mutation and produces an individual with both the original mutation and suppressor mutation

How do substitutions occur?

in spontaneous chemical changes

Flexible DNA structure

How do insertions and deletions occur?

strand slippage

DNA repair

DNA ligase

DNA polymerase

Mismatch repair

Base-excision repair

Nucleotide-excision repair

Direct repair

Which enzymes carry out base-excision repair?

Glycosylase enzymes

aneuploidy

duplication of whole chromosomes

polyploidy

duplication of whole genomes - can cause instant speciation

pseudogenes

former genes that have accumulated mutations and are nonfunctional

Reciprocal translocation

reciprocal exchange of segments between two nonhomologous chromosomes

C-value paradox

lack of correlation between genome size and the biological complexity of an organism