Mutation Flashcards
What is a misense mutation?
When one amino acid is substituted for another, usually by a single base pair substitution .
What is a frameshift mutation?
The open reading frame is altered in some way, usually occurs after insertions and deletions.
What is a silent mutation?
A single base change that does not substitute the amino acid.
What is a conservative misense mutation?
When an amino acid change is fairly well tolerated by a protein, eg alanine to valine in a fairly non critical region.
What often happens after a insertion or deletion that causes a frame shift?
A premature stop codon will be generated creating a premature termination site, and these shorter proteins will be degraded by nonsense mediated decay.
How can the process of tautomeric shift lead to mutations?
This is where a proton briefly changes position in a base, and this rare form will have altered base pairing properties, which can behave s an altered template base during replication. In the tautomeric forms c will pair with a and t will pair with g.
How can slippage during replication lead to mutation?
If the newly synthesised strand loops out during replication, there is the addition of one nucleotide and if the template strand loops out, this results in the omission of one nucleotide in the strand.
How can nitrous acid cause mutation?
Can replace the amino group of an base with a keto group, causing c to transform to uracil, which paris with alanine, a to hypoxyalanine which pairs with c, and g with xaline that pairs with c.
How can ethylmethylsuphonate cause mutation?
It causes the rmoval of purine rings, and an aprinic base can be paired with anything.
Give an example of a base stacking mutagen?
2-amino-3-methyl limidazo (4,5 -f) which is a heterocyclic, aromatic amine.
How do base stacking mutagens cause mutation?
They cause mostly single deletions at GC base pairs, and disrupts the stacking of the DNA molecule.
Describe the process of excision repair.
DNA can acculmulate damaged bases, which are either oxidised, alkylated or just become uracil, which is repaired by excision repair.
Describe the process of nucleotide mismatch repair.
Enzymes detect mismatched bases in a newly synthesised DNA strands, and replaces these with a patch of new DNA (not just a single base)
How can UV light affect mutation.
Can lead to thymine dimer formation, where photons cause adjacent photons to bond with one another, and can often be resolved spontaneously through the process of photoaction.,
How are DNA repair and cancer linked?
Cancer often results from a failure in DNA repair mechanisms, human genes such as MLH1, MSH p6 MSH2 encode mismatch repair enzymes and are commonly mutated in cancer (heredrity nopnpolyplasia corectal cancer)
