Mutations Flashcards
Define mutation.
A change of nucleotide sequence.
What is mutagenesis?
The process of mutation generation.
What is deamination?
A mutation where C for example is turned into U.
Why might deamination not be a problem if C - G is turned into U - G?
Because during replication U - G might be replicated into C - G. This turns out to be completely fine because the that was the combination from the beginning.
However if U - G is replicated into U - A it might end up being replicated again into T - A. T - A is a completely different combination that can cause problem.
Give some exogenous sources of mutation.
Ionising radiation Environment Free radicals Mutagenic chemicals Anti-cancer agents
Give some endogenous sources of mutation.
DNA replication defects like deamination, mismatching etc.
Transposable elements.
What are transposable elements or also called transposons?
They used to be called jumping genes.
They are specific DNA sequences that can move to random sites on its DNA molecule.
Why can transposons cause a problem?
If they hop onto a part of the DNA sequence where it inactivates a gene or changes gene expression causing a mutation.
How does the size of a gene relate to the risk of transposons affecting them?
The bigger the gene the higher risk of a transposon hopping onto it and either activating it or inactivating it.
What are some positive outcomes of mutations?
It is a source of genome variation
It is a driving force of evolution
What is a SNP mutation?
Single nucleotide polymorphism when one single nucleotide is affected and altered/switched out or deleted/inserted.
Define anonymous SNP.
A SNP that doesn’t appear to have any effect.
Define non-coding SNP.
When SNP occurs outside a gene as it not coded for.
Define coding SNP.
When SNP occurs inside a gene and is coded for. This is the worst one.
On a micro scale (nucleotide scale) what is deletion, insertion and substitution?
Deletion is when a nucleotide is deleted so the sequence has one less nucleotide.
Insertion is when a nucleotide is inserted so the sequence has one more nucleotide.
Substitution is when one nucleotide is swapped into another nucleotide.
What are the mutations that can happen on a macro scale (chromosomal level)? Explain them briefly.
Deletion
Duplication
Inversion (a part of the chromosome is put upside-down)
Substitution (a part of the chromosome is put on another chromosome)
Translocation (two parts, one on each chromosome are swapped)
How is DNA read in transcription? How is mRNA synthesised?
Read 3’ to 5’
Made 5’ to 3’
How is mRNA read in translation? How is the polypeptide chain synthesised?
Read in 5’ to 3’
Made in N to C
Regarding SNP and substitution; what is transition?
When the base is changed to the same type. This means a purine goes to a purine (A G) or a pyrimidine goes to a pyrimidine (T C)
Regarding SNP and substitution; what is transversion?
When the base is changed to a different type. This means that a purine is changed to a pyrimidine or vice versa. (A T or C G)
What are some consequences of single nucleotide changes?
It can change the gene product (polypeptide or RNA)
It can change the amount made of the gene product
It can change the polypeptide length
It might not have an effect at all
Sickle cell anaemia is a mutation in the 7th codon of the HBB gene. Why is it said that the 6th amino acid is changed from glutamate to valine?
This is because codon 1 is the start codon methionine which is chopped off.
Sickle cell anaemia is a missense base substitution mutation where GAG goes to GTG. What would is the difference in the mRNA product?
GAG is supposed to make an mRNA that is GAG this means it’s read from CTC.
GTG instead makes GUG because what is read is the other strand which is no longer CTC but CAC instead.
What is a missense mutation?
A mutation which results in a codon that codes for a different amino acid. It is a type of non-synonymous mutation.
