Chapter 13 Mutation and DNA repair

Mutation

A heritable change in genetic material.

Point mutation

A mutation that affects only a single base pair within the DNA.

Base substitution

A type of point mutation where one base is replaced by another.

Silent mutation

A point mutation that does not change the amino acid sequence of a polypeptide.

Missense mutation

A point mutation that changes one amino acid in the polypeptide chain.

Nonsense mutation

A point mutation that creates a premature stop codon in the polypeptide.

Frameshift mutation

A mutation caused by insertion or deletion of nucleotides that alters the reading frame.

Somatic cells

All body cells except germ-line cells; mutations here are not heritable.

Germ-line cells

Cells that give rise to gametes; mutations can be passed to offspring.

Mutagen

An environmental agent that causes mutations.

Spontaneous mutation

A mutation that occurs naturally due to errors in biological processes.

Induced mutation

A mutation that results from exposure to external agents, such as chemicals or radiation.

Ames test

A test that determines if a substance is a mutagen by analyzing its effect on mutant Salmonella bacteria.

Nucleotide excision repair (NER)

A DNA repair system that removes damaged nucleotides and replaces them with the correct ones.

Cancer

A disease caused by gene mutations that lead to uncontrolled cell division.

Chemical mutagens

Agents that cause mutations through covalent modifications or acting as base analogs.

Physical mutagens

Environmental agents such as X-rays and UV light that can damage DNA structure.

Thymine dimers

A type of DNA damage caused by UV light where two adjacent thymine bases bond together.

DNA replication error

A type of spontaneous mutation that occurs when DNA is copied incorrectly.

Background mutation rate

The average rate at which spontaneous mutations occur in a genome.

Repair systems

Biological mechanisms that detect and repair DNA damage to minimize mutations.