Mutations

Mutation

Change in the genetic material

Mutations may be

neutral, beneficial, or harmful

Mutagen

Agent that causes mutations

Spontaneous mutations:

Occur in the absence of a mutagen

Base Substitution (Point Mutation)

A change in one base

Silent Mutation

A change in codon but no change to the amino acid (because each amino acid has multiple codons that code for it)

• neutral

Missense Mutation

A type of point mutation

• results in a change in amino acid from a change in nucleotide

• could be positive or negative

Nonsense Mutation

Results in a stop codon before there should be

• “nonsense” because the protein hasn’t been fully created - it means nothing

Frameshift Mutation

Insertion or deletion of one or more nucleotide pairs

• catastrophic disruption to protein

• results in completely different proteins because there are completely different amino acids in the sequence

Ionizing radiation (x-rays and gamma rays)

cause the formation of ions that can react with nucleotides and the deoxyribose phosphate backbone

Thymine dimer

disrupt in DNA caused by adjacent thymine bases that became crosslinked and disrupt normal base pairing

• caused by ionizing radiation

Repairing mutations

• an enzyme cuts out the damaged DNA and DNA polymerase fills the gap by synthesizing new DNA using the intact strand as a template

• DNA ligase seals the remaining gap by joining the old and new strands