The Mechanism Of Mutation Flashcards
What are the 2 types of mutations
Germ-line mutations (when the entire organism is affected and the gametes have the mutation) and somatic mutations (mutations occurring in somatic cells and the gametes do not carry the mutation)
How can mutations occur?
When there are mistakes in DNA replication.
Mutations can be caused by environmental factors.
Can be caused by transposomes (factors that insert them selves into the genome)
What are the replication errors that can lead to mutations
Substitutions: which can be transitions (adenine with guanine/ cytosine with thymine) or transversions(adenine with cytosine)
Insertions/deletions and instability of tandem repeats. This is due to a slippage which causes the insertion of more nucleotides
Define mutation. What are the 2 kinds of mutations?
It is the permanent change in the sequence of DNA. They can be spontaneous (due to the structure of DNA, can be depurination or deamination) or induced( can be chemical or physical)
Explain the spontaneous mutation : deamination. Which base doesn’t undergo this process?
It is the hydrolysis of an amino group, it can take place in all N bases, the most common it the transformation of cytosine into uracil. Thymine does not undergo deamination
5-methyl cytosine spontaneously deaminates into ? What happens next
Thymine . This occurs when C follows a G (a methyl group is added onto the C5 of cytosine). Because uracil is not present in the DNA a mechanism recognises uracil and substitutes it for Cytosine.
Name a hotspot mutation
When the CG is converted into TG. This has caused a decrease in the CG bonds present in the genome, thus the naming of CpG islands : Is where there is the predicted amount of CG, they are close to the 5’ of genes,
How is the CpG into TpG mutation fixed?
The double strand of DNA will not match perfectly, so we will have a mismatch and there is a mechanism present to fix this
Explain single strand breaks?
When 1 of the 2 DNA strands are broken, this Nick doesn’t change the DNA molecule much, as there are H bonds keeping the two stands together. When there are 2 breaks, the fragments of DNA molecule begin drifting apart and they may not replicate properly. Telomeres try to join them together
Explain the induced mutation : Chemical
It can be exogenous or endogenous: ROS which are produced by metabolism. Alkylating substances (substances that can transfer methyl, ethyl groups to bases or the backbone of phosphate groups), polyaromatic hydrocarbons, ROS, base analogue pairs, intercalating agents.
Polycyclic aromatic hydrocarbons describe them
They have a ring structure, are sourced by everywhere, are formed when organic material containing Carbon are burned.
Describe the Ames test
It is a test that determines what is a mutagen and what isn’t. Go to notes
Explain the induced mutation: Base analogues
Are mutagenic, go form a keto to enol form
Explain the induced mutation: intercalating agents
Eg: ethidium, bromide, proflavin, acridine orange
They are molecules that can embed between the molecules of DNA causing insertions or deletions
Explain the physical mutation caused by UV light
Go to notes and slides
