Mutations Flashcards
What is a mutation?
A heritable alteration in a gene or sequence
Mutations can arise through either _________ or _______ sources
Endogenous
Exogenous
Give examples of exogenous causes of mutations
Ionising radiation
Anti-cancer agents
Mutagenic chemicals
Where does the majority of ionising radiation come from?
Natural sources e.g. Radon gas
What are two endogenous causes of mutations?
DNA replication defects
Transposable elements
What are transposable elements? How can this result in a mutation?
Specific DNA sequences which act as ‘jumping genes’ and move as a unit to random sites
It could result in the transposable element placing itself into the sequence of an active gene and changing its sequence and thus inactivating it
What are micro mutations?
Single base mutations e.g. Insertion, deletion, substitution
What are macro mutations?
Concerning dna sequences or whole genes
Can be insertions, substitutions, deletions or translocations
A single nucleotide change can either be a transition or a transversion, what is the difference between the two?
Transition = change to the same type of base (e.g. Purine to purine)
Transversion = change to a different type of base (purine to pyrimidine)
Sickle cell anaemia is as result of which base change? And therefore which amino acid change?
A to T
Glutamate to valine
Which codon and amino acid is mutated in sickle cell anaemia?
Codon 7
Amino acid 6
What is a missense mutation?
Where a base change results in a change of amino acid
What is a natural/silent/synonymous mutation?
Where a single base mutation results in the sam amino acid and same phenotype being produced
Which single nucleotide changes can affect the polypeptide length?
Additions or deletions (frameshift mutations)
Mutations of the stop codon
Nonsense mutation
What is a nonsense mutation?
Where a single base change results in a stop codon being formed
Which two single nucleotide changes can result in a frameshift mutation?
Deletion
Addition
What mutations can base substitutions result in?
Missense mutations
Nonsense mutations
Synonymous mutations
Give two ways in which mutations can change the amount of gene product formed?
Can affect promoter activity
Can affect mRNA splicing
Can alter translation initiation at AUG
Chromosomal mutations are most damaging when they occur in which cells?
Germ line cells
What cells are affected by germ line cell mutations? Can they be passed on to offspring?
All cells in the body
Can be passed to offspring
What are somatic mutations? Can they be passed onto offspring?
Mutations in a body cell
No
Do RNA polymerases have proofreading mechanisms?
No
Why are RNA mutations not as damaging as DNA mutations?
RNA is degraded quickly
Not inherited
Multiple copies of RNA are made
Mitochondrial dna mutations in germ line cells can often result in conditions that affect…
Multiple organ systems
What are the repair mechanisms for mtDNA like?
Mitochondrial DNA has limited ability to repair itself —> so mutations build up
Build up of mtDNA mutations is a likely contributor to?
Ageing
Associated with cancer, heart disease etc.
Most errors in mitosis usually occur in which stage?
Metaphase
What is a common pattern seen when looking at recessive mutations?
They usually lead to loss of function and affect biochemical pathways
What is the common pattern seen amongst dominant mutations?
Usually lead to increased function and lead to structural abnormalities
