7: Mutation, Repair, & Transposable Elements Flashcards
Adaptive mutation hypothesis
Environment causes heritable change
What is the spontaneous random mutation hypothesis?
Mutation occurs by chance and not in response to the environment
What did luria and delbruck do?
They performed a fluctuation test, disproving the hypothesis of adaptive mutation
Mutation rate =
Change/nucleotide/generation
Eukaryotic mutation rate
10^-4 and 10^-6
Bacteria/phage mutation rate
10^-6 and 10^-8
Transition mutations
Purine –> purine
Pyrimidine –> pyrimidine
Transversion mutations
Pyrimidine –> purine
Purine –> pyrimidine
Is transition or transversion more common?
Transition
What is a missense mutation?
A change from one amino acid to another
What is a nonsense mutation?
A change from an amino acid to a stop codon
What is a neutral mutation?
A change from an amino acid to another amino acid with similar chemical properties
What is a silent mutation?
A change in the codon such that the same amino acid is coded for
2 types of reversion mutations
- True reversion
2. Partial reversion
True reversion
Mutant to wild type ( identical amino acid seq)
Partial reversion
Changes in other amino acid that fully or partially restores protein function
suppressor mutations
Occur at sites different from the mutations they suppress
Intragenic suppressor
A suppressor that occurs within the same gene as the original mutation, but at different sites
Intergenic suppressor
At mRNA translation level
Each suppressor works on only one type of nonsense, missense, or frameshift mutation
Nonsense suppressors
In redundant tRNA genes
Occurs by competition between release factor and suppressor tRNAs
At which phase of the cell cycle do mutations occur?
S phase
7 factors that effect mutation rate
- Spontaneous isomerization due to reversible proton shift
- Base analogs
- Genetic constitution of organism
- Repetitive nucleotides, cg islands, pyrimidine dinucleotides
- DNA polymerase proof-reading functions
- DNA repair
- Selection
Base substitution
Enol OH can form H bond w/ incorrect partner
Which nucleotide does G wobble base pair with?
T
