Week 10 - Cell Cycle and Division (Mutations) Lecture 2 Flashcards
What are germline mutations
mutations which occur in the germline e.g. gametes, sperm, egg (passing it on to off springs)
What are somatic mutations
Mutations which do not occur in the germline e.g. brain, skin, liver
How do environmental and genetic factors impact mutations
They can increase the rate of the natural basal rate of mutation
What are some things which can cause mutations
- Radiation
- Chemical Agents
What are 5 types of mutations
- Point mutation
- Deletion
- Duplications
- Inversions
- Translation and transposons
What is point mutation
One nucleotide has changed into another e.g. G has been shifted into a C
(single Nucleotide polymorphism)
What is deletion as a type of mutation
One or more nucleotides are removed from the DNA sequence, causing a frameshift mutation and potentially altering the amino acid sequence
What is duplication as a type of mutation
Doubling of a segment of DNA, resulting in the presence of two or more copies of the same genetic material
What is inversion as a type of mutation
Nucleotide/s swap order
What is translation and transposons as a type of mutation
Exchange of genetic material between non-homologous chromosomes. This can lead to gene fusions, altered gene expression, or chromosome rearrangements, contributing to cancer and other genetic disorders.
What is an example of translation and transposons
Between chromosome 9 and chromosome 22, the ABL gene from 9 breaks off and joins onto the BCR gene on 22. BCR acts as an on switch causing uncontrolled cell division.
*BCR fusion protein is only present if there is an issue with the DNA and mostly likely an indicator of cancer
What are some rare types of mutations
- Spice site mutation
- Replication slippage
- Amplification
What is splice site mutation
Insertion or deletion of nucleotides in a region (either intron or exon) which regulates exon splicing order
What is replication slippage
Increasing number of trinucleotide repeats
Newly synthesized strand may contain an insertion or deletion of one or more repeat units compared to the template strand.
What is amplification as a type of mutation
A region of DNA is inappropriately replicated e.g. accidently duplicating an extra chromosomes
What are the different mutation outcomes (6)
- Synonymous mutation
- non-synonymous (missense) mutation
- nonsense mutation
- conservative mutation
- non-conservative mutation
- frameshift
What are synonymous mutations
A mutation which doesn’t change the amino acid. This can occur as there is redundancy within the genetic code and some nucleotide sequences can produce the same amino acid. Eg. changing CUU into CUC will still produce Leu.
What are non-synonymous (missense) mutation
A mutation which changes the amino acid. E.g. CUU changing into CCU
What are nonsense mutations
A mutation which changes the amino acid to a STOP codon. This results in a truncated protein chain.
What are conservative mutations
A mutation which changes the amino acid, however the new amino acid has similar biochemical properties (e.g. charge, hydrophobicity and size)
What are non-conservative mutations
The new amino acid does not have similar biochemical properties
what are frameshifts as a mutation outcome
An insertion or deletion of nucleotides which is not divisible by 3. This will cause a frameshift and alter all of the amino acids produced as
1 frame = 3 nucleotides = 1AA
What are the different ways which the function of a cell can be impacted due to mutation
- No functional change
- Loss of Function - the most common outcome (99%)
- Gain of Function - much rarer e.g. SARS-Cov2
What are the 2 main types of genes which when mutated can lead to cancer
oncogenes
tumour-suppressor genes
