Genetics Lecture: Gene Mutations, Types, Mechanisms, and Effects

Flashcards testing core vocabulary regarding types of gene mutations, mutation mechanisms, mutagen types, and biological consequences from Chapter 1 to Chapter 8 of the lecture transcript.

Forward Mutation

A mutation that changes a wild-type phenotype into a mutant phenotype, often used experimentally via gene knockouts (KO) to determine gene function.

Reverse Mutation

A mutation that restores a mutant phenotype back to the wild-type genotype, often studied using gene knock-ins (KI).

Synonymous Substitution

A base substitution (also called a silent substitution) that alters a codon without changing the encoded amino acid.

Nonsynonymous Substitution

A base substitution that alters the codon sequence to code for a different amino acid or a stop codon.

Missense Mutation

A type of nonsynonymous substitution where a single base change alters a codon to code for a different amino acid.

Nonsense Mutation

A type of nonsynonymous substitution that changes an amino-acid-coding codon into a stop codon, prematurely terminating protein synthesis.

Neutral Substitution

A mutation that changes an amino acid in a peptide sequence without altering the overall function of the resulting protein.

Frameshift Mutation

An insertion or deletion of nucleotide bases (not in multiples of three) that alters the translational reading frame of downstream codons.

Indels

A shorthand term used to describe insertion or deletion mutations in a DNA sequence.

Trinucleotide Expansion

A mutation mechanism where repetitive three-base codons increase in copy number, forming DNA hairpins and causing conditions such as ALS and Huntington's disease.

Spontaneous Mutagenesis

Mutations that occur naturally and randomly due to internal biological or chemical processes without external mutagen exposure.

Induced Mutation

A mutation resulting from exposure to an external physical or chemical agent known as a mutagen.

Depurination

A spontaneous mutation mechanism in which a purine base (adenine or guanine) breaks off from its sugar-phosphate backbone.

Deamination

The removal of an amino group from a nitrogenous base, such as converting cytosine into uracil, which alters pairing during DNA replication.

Base Tautomerization

A phenomenon where protons randomly shift within a nitrogenous base molecule, creating rare structural forms (tautomers) that lead to anomalous base pairing.

Strand Slippage

An error during DNA replication where DNA polymerase slips on repetitive base runs, leading to single-base insertions or deletions.

Intercalating Agents

Chemical compounds (such as ethidium bromide or proflavine) that wedge between adjacent DNA base pairs, causing insertion or deletion mutations during replication.

Germline Mutation

A mutation occurring in gametes or gamete-producing cells, which is transmitted to offspring and affects every cell in the offspring's body.

Somatic Cell Mutation

A mutation occurring in non-reproductive body cells, affecting only a localized population of cells in the individual and not passed on to offspring.