BI 321 Genetics: Gene Mutation and DNA Repair

These flashcards cover key concepts related to gene mutation and DNA repair as discussed in Chapter 19 of BI 321 Genetics.

Mutation

A change in the DNA sequence that can affect gene function.

Point Substitution

A mutation where a single nucleotide is changed to a different nucleotide.

Types of Point Substitutions

Transition (purine to purine, pyrimidine to pyrimidine) and Transversion (purine to pyrimidine, pyrimidine to purine).

Insertions and Deletions

Types of mutations that can result in frameshifts, affecting the coding sequence of DNA.

Nonsense Mutation

A mutation that introduces a premature stop codon in the coding sequence.

Frameshift Mutation

A mutation caused by insertions or deletions that shifts the reading frame of the gene.

Silent Mutation

A change in the DNA sequence that does not alter the amino acid sequence of the resulting protein.

Missense Mutation

A mutation that results in a different amino acid being incorporated into the protein.

Mutations Outside Coding Sequences

Mutations that can occur in non-coding regions, such as regulatory elements or introns.

Suppressor Mutations

Mutations that counteract the effects of a previous mutation, restoring function.

Position Effect

A phenomenon where the location of a gene affects its expression due to surrounding genomic context.

Spontaneous Mutations

Mutations that occur without external influence, often due to errors in DNA replication.

Chemical Changes During Spontaneous Mutations

Examples include base modifications, depurination, and deamination.

Oxidative Stress and DNA

Can cause damage such as base modifications and strand breaks, affecting DNA integrity.

Trinucleotide Repeats

Repeated sequences that can expand during DNA replication, leading to instability and mutations.

Chemical Mutagens

Substances that induce mutations by causing various types of DNA damage, including base pairing errors.

UV Light Effects on DNA

Can cause pyrimidine dimers, disrupting normal base pairing and DNA replication.

Mutagenicity Testing in Bacteria

Assessment of mutagens by observing mutations induced in bacterial strains, such as the Ames test.

DNA Repair Mechanisms

Cellular processes that correct DNA damage and maintain genome stability.

Direct Repair

A repair process that directly reverses DNA damage, such as photoreactivation of thymine dimers.

Base Excision Repair (BER)

A repair mechanism that corrects single-base lesions through the removal and replacement of damaged bases.

Nucleotide Excision Repair (NER)

Repairs bulky DNA adducts and helix-distorting lesions by excising a short single-stranded DNA segment.

Mismatch Repair

Corrects DNA replication errors that escape proofreading by recognizing and repairing mismatched bases.

Homologous and Non-Homologous End Joining

Mechanisms to repair double-strand breaks; homologous uses a sister chromatid while non-homologous directly joins ends.

Translesions

DNA sequences that are synthesized across sites of damage, often leading to mutations.