Mutations Flashcards
Somatic vs Germline mutations
Somatic only impacts the individual, not heritable. Germline impacts offspring, heritable.
Base substitutions are either
transitions (purine replaces purine, etc) or transversions (purine replaces pyrimidine, etc)
insertions and deletions can cause
frameshift mutations. leads to dysfunctional proteins
how are expanding nucleotide repeats made? how do they get worse?
a hairpin forms between repeating sequences and so the sequence is replicated twice. The longer strand is now the template and so the repeats continue to get longer with more replication and the disease gets worse.
Phenotypic effects of mutations
missense: amino acid replaced by different amino acid
nonsense: sense codon replaced by nonsense (stop)
silent: codon replaced by synonymous codon
neutral: missense with no change in function
mutations can lead to…
loss of function, gain of function, or death (lethal mutations)
what are suppressor mutations? what are the types?
a mutation that hides or suppresses the effect of another mutation. Intragenic takes place on the same gene as the original mutation, intergenic occurs on a gene other than the original mutation.
Spontaneous replication errors
Non-typical pairing can happen due to tautomeric shifts, wobble pairing, and strand slippage. Newly synthesized strand slip causes addition and parent strand slip causes deletion.
What is a mutagen?
any environmental agent that can increase mutation rate above what is expected by spontaneous mutation
Radiation causes what kind of problem?
Thymine dimers. Two thymine bases covalently bond and block replication, causing death.
Ames test
testing for cancer (mutation) causing chemicals (mutagens). Uses mutated bacteria strains that will appear much more on mutagenic compounds
Transposable elements: what are they? what can they cause? what are their features?
sequences that can move about the gene. can cause mutations. 2 features: flanking direct repeats and terminal inverted repeats.
What is the difference between an insertion sequence and composite transposons?
Insertion sequences are the simplest type, they have one set of inverted repeats and one set of flanking direct repeats.
Composite transposons are segments of DNA that become flanked by two copies of an insertion sequences may transpose
When would you need mismatch repair vs. nucleotide-excision repair? How does direct repair differ from those two?
mismatch is for an incorrectly inserted base, nucleotide-excision is for DNA lesions like thymine dimers. Direct repair is different because it does not replace nucleotides, it restores them
Mismatch repair
incorrectly inserted nucleotides will be corrected, a complex cleaves the mismatch and it is replaced
