S9) Introduction to DNA Mutation Flashcards
What is a mutation?
A mutation is a heritable alteration in a gene or chromosome (a change in the sequence of nucleotides) and also the process that produces the alteration
Identify two sources of exogenous mutations
- Ionising radiation/particles and free radicals
- Mutagenic chemicals and anti-cancer agents
What is the general effect of exogenous mutagens?
Exogenous mutagens lead to defective/error-prone DNA repair in the body
identify 6 processes/substances which lead to the formation of free radicals
- UV light
- Ionising radiation
- Smoking
- Air pollution
- Inflammation
- Metabolism
What are the two sources of endogenous mutations?
- DNA replication errors
- Transposable elements
What are transposable elements?
A transposable element is a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell’s genetic identity and genome size
Identify 4 types of micro mutations (DNA)
Identify 5 types of macro mutations (chromosomal)
What are the four different types of single nucleotide changes?
- Mutations that change gene products
- Mutations that change the amount of gene product
- Mutations that change the polypeptide length
- Mutations that have no effect
What are missense mutations?
Missense mutations are mutations which change the gene product due to a change in amino acid
Identify some types of mutations which change the polypeptide length
- Frameshift mutations
- Mutations of stop codon
- Nonsense mutations
Mutations that change the amount of gene product affect transcription and/or translation.
Identify some examples
- Alter promoter activity
- Alter translation initiation at AUG
- Prevent mRNA splicing
- Reduce mRNA stability
What are silent mutations?
Silent/neutral mutations are mutations which have no effect
What are the different types of substitutions?
- Transition: change to same type of base e.g. purine to purine (A ⇒ G)
- Transversion: change to different type of base e.g. purine to pyrimidine (A/G ⇒ T/C )
What is sickle cell anaemia?
Sickle cell anaemia is a haemoglobinopathy which arises due to a single base mutation in the β-chain of haemoglobin (Glu ⇒ Val) causing the blood cells to become rigid and sickle (HbS protein)
