Mutations Flashcards
What is the most common type of SNP?
C to T change
What is a transition SNP?
When 2 bases that are the same size are swapped (eg. 2 purines)
What is a transversion SNP?
Bases that are different sizes are swapped (eg. a purine and a pyrimidine)
What position in a triplet is a SNP unlikely to cause any change?
3rd position (wobble position)
What is a missense mutation?
1 amino acid is substituted by another, normally a SNP
What is a silent mutation?
A single-base mutation which does not substitute the amino acid
What is a non-sense mutation?
An amino acid codon is mutated to a stop codon
What is a frameshift mutation?
The reading frame of the mRNA is altered due to an insertion, a deletion or a premature stop codon.
What is a conservative missense mutation?
Amino acids with similar properties may have no consequence if substituted for each other.
What will happen to the reading frame if 3 bases are inserted or deleted?
Nothing. The reading frame is not disrupted
How are nonsense mutations causing premature termination codons (PTC) degraded?
Nonsense mediated decay (NMD)
List 3 causes of DNA base changes
Sequence changes in DNA replication
Chemicals
Radiation
What is a tautomeric shift?
A proton briefly changes position in a base during replication. This results in altered base-pairing properties and so acts as an altered template in DNA replication.
What occurs in ‘slippage’ during replication?
When there is a run of the same base, in replication, the newly synthesised strand can loop out resulting in the addition of a nucleotide. This causes a frameshift mutation.
How does the mutagen IQ work?
Disrupts the packing of DNA bases and causes single base deletions. It forces the bases further apart
Name 3 sources of radiation
Sun
X-rays
Nuclear power plants
Environmental sources- granite, radon gas
How does UV light damage DNA?
It causes adjacent thymine bases to pair with each other
What is mismatch repair?
Enzymes detect mismatched bases in newly synthesised strands and replace the bases
What is base excision repair?
Accumulations of damaged bases can be removed at once
What results when DNA repair mechanisms fail?
Cancer
What is an oncogene?
Mutated proto-oncogenes which result in excessive cell replication
How can foetal DNA be obtained?
Amniotic fluid cells
Chorion villus biopsy
Foetal DNA in the mother’s blood
What test is used to perform exon counts for many exons in parallel?
MLPA
What is a single nucleotide polymorphism (SNP)?
Single-base substitutions
