Genetic Mutations - CHP 12

Vocabulary flashcards covering key mutation concepts, types, mechanisms, and repair from the notes.

Mutation

A change in the DNA sequence, occurring spontaneously or due to mutagens, that can alter gene function and contribute to genetic diversity.

Mutation rate

Frequency at which mutations occur per genome per generation; typically low and varies among organisms and genes.

Germ-line mutation

Mutation that occurs in germ cells (sperm or egg) and can be inherited by the next generation.

Somatic mutation

Mutation that occurs in non-germ cells and is not passed to offspring; can be propagated to descendant cells by mitosis.

Mutation hotspot

A region of the genome with an elevated mutation rate, often due to factors like large gene size.

Dominant mutation

A mutation whose phenotype is expressed in a single copy, making it easier to detect.

Recessive mutation

A mutation whose phenotype appears only when two copies are present (both alleles mutated).

Gene mutation

Any alteration in the DNA sequence of a gene, including substitutions, insertions, or deletions.

Point mutation

Localized mutation at a specific, identifiable position in a gene; includes base-pair substitutions.

Base-pair substitution

Replacement of one nucleotide base pair with another in the DNA sequence.

Transition mutation

A base-pair substitution where a purine replaces a purine (A↔G) or a pyrimidine replaces a pyrimidine (C↔T).

Transversion mutation

A base-pair substitution where a purine is replaced by a pyrimidine or vice versa (e.g., A or G ↔ C or T).

Silent mutation

A base-pair change that does not alter the encoded amino acid due to genetic code redundancy.

Missense mutation

A base-pair change that alters the amino acid sequence of the protein.

Nonsense mutation

A base-pair change that creates a stop codon, terminating translation prematurely.

Frameshift mutation

Insertion or deletion of nucleotides that shifts the reading frame, usually altering downstream amino acids and often terminating early.

Promoter mutation

Mutations in promoter regions that alter transcription initiation and level.

Splice-site mutation

Mutations at intron–exon splice sites that disrupt normal RNA splicing.

Cryptic splice site

A newly created or activated splice site from a mutation that alters mRNA processing.

Polyadenylation mutation

Mutation in the polyadenylation signal (AAUAAA) affecting 3′ end processing of mRNA.

Regulatory mutation

Mutations in non-coding regions that alter the timing or amount of transcription.

Forward mutation

Mutation that converts a wild-type allele to a mutant allele.

Reversion mutation

Mutation that restores the wild-type or near wild-type phenotype from a mutant allele.

True reversion

A second mutation at the same site that restores the original DNA sequence and function.

Intragenic reversion

Reversion caused by a second mutation within the same gene that restores function.

Second-site (suppressor) reversion

A mutation in a different gene that compensates for the original mutation’s effect.

Ames test

A bacterial mutagenicity assay using Salmonella with histidine dependency, tested with metabolic liver enzymes (S9).

Mutagen

An agent that causes DNA damage leading to mutations.

Nucleotide base analog mutagen

A chemical mutagen that mimics DNA bases and causes base-pair substitutions.

Intercalating agent

A chemical mutagen that inserts between base pairs, often causing frameshift mutations.

Tautomer

Alternate forms of nucleotides with different base-pairing properties, leading to mispairing during replication.

Depurination

Loss of a purine base from DNA, creating an apurinic site that can cause mutations during replication.

Apurinic/apyrimidinic (AP) site

A site in DNA missing a purine or pyrimidine; often filled by incorrect nucleotides if unrepaired.

Deamination

Loss of an amino group from a nucleotide (e.g., C to U), which can cause mispairing and mutations if not repaired.

5-methylcytosine deamination

Deamination of 5-meC to thymine, creating a G-T mismatch that may be misrepaired or fixed as mutation.

DNA repair

Cellular systems that fix DNA damage either directly or by removing and replacing damaged segments.

Mismatch repair

Repair pathway that corrects mispaired bases after DNA replication.

Nucleotide excision repair

Repair pathway that removes bulky DNA lesions, such as UV-induced photoproducts.

DNA damage signaling

Cellular networks that detect DNA damage and activate repair processes during the cell cycle.

Li-Fraumeni syndrome

Hereditary cancer predisposition caused by mutations in the p53 tumor suppressor gene.

p53

A key tumor suppressor gene that orchestrates the cellular response to DNA damage.

ATM

A gene encoding a kinase; mutations cause ataxia telangiectasia and affect DNA damage response.

BRCA1

A DNA repair gene; mutations raise risk of breast and ovarian cancer.

Xeroderma pigmentosum

DNA repair disorder with extreme sensitivity to UV light and high skin cancer risk.

Trinucleotide repeat expansion

Increase in the number of trinucleotide repeats in a gene, often causing disease when exceeding a threshold.