Chapter 11 - Gene Mutation, DNA Repair, and Homologous Recombination

What is the mutation rate?

rate at which mutations occur per gene per unit of time; most often expressed per gene per generation

What are the two ways mutation rate can be mueasure?

counting the number of mutation affecting a phenotype; determining the frequency of mutations per base pair

What are mutation hotspots?

location within a gene or genome at which mutations occur much more often than average

What is the fluctuation test and what did it prove?

experiment that identified the random nature of gene mutations

What is the random mutation hypothesis?

predicted that different bacterial cultures would develop resistance mutations at different times, yielding variable numbers of resistant bacteria

What is the adaptive mutation hypothesis?

disproved theory of the source of gene mutations proposing that mutated copies of genes were available in the genome or could rapidly occur in the genome given specific changes in the physical environment of an organism

What are germ-line mutations?

mutations that occur in germ-line cells (sperm and egg); can be passed from one generation to the next

What are somatic mutations?

mutations in somatic cells; only direct descendants of the mutated cell will carry mutation

What are point mutations?

occur at a specific position in a gene or a specific location anywhere in genome; have varied consequences depending on the type of sequence change and location of affected part of the gene

What are base-pair substitution mutations?

replacement of one nucleotide base pair by another

What are transition mutations?

one purine replaces another, or one pyrimidine replaces another

What are transversion mutations?

a pyrimidine is replaced by a purine or vice versa

What is a synonymous mutation?

base pair change that does not alter the resulting amino acid due to the redundancy of the genetic code

What are missense mutations?

base pair change that results in an amino acid change in the protein

What are nonsense mutations?

base pair change that creates a stop codon in place of a codon specifying an amino acid

What are frameshift mutations?

insertion of deletion of one or more base pairs leads to addition or deletion of mRNA nucleotides

What are regulatory mutations?

point mutations that alter the amount, but not amin oacid sequence, of protein product produced by gene

What are the different types of regulatory mutations?

promoter mutations, splicing mutations, and cryptic splice sites

What are promoter mutations

alter consensus sequence nucleotides of promoters; interfere with efficient transcription initiation; can cause mild to moderate reductions in transcription levels and some may abolish transcription

What is a splicing mutation?

mutation that alters the normal splicing pattern of a pre-mRNA; can result in splicing errors of introns and production of mutant proteins

What is a cryptic splice site?

base-pair substitution mutations that produce new splice sites that replace or compete with authentic splice sites during mRNA processing

What are polyadenylation mutations?

mutation of the polyadenylation signal sequence at the 3’ end of eukaryotic mRNA can block proper 3’ processing of mRNA

What is a forward mutation?

converts a wild-type allele to a mutant allele

What is a reverse mutation/reversion?

converts mutant alleles to wild-type or near wild-type allele

What is true reversion?

wild-type DNA sequence is restored by a second mutation within the same codon

What is intragenic reversion?

occurs through second mutation elsewhere in the same gene

What is second-site reversion/suppressor mutations?

occurs by mutation in a different gene that compensates for the original mutation, restoring the organism to wild-type