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16 Cards in this Set

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Mutation
Mutations are the changes in the genome of an organism. They occur spontaneously and are inevitable. Few mutation are advantageous, most are neutral or deleterious.
Mutations may result from:
- Mistakes in DNA replication;
- Damage: radiation, chemical mutagens.
- Insertion or transposon (mobile genetic element).
Do mutations outside coding regions lead to any changes?
Yes, they lead to phenotypic changes if they alter gene expression, e.g. reduce the level of transcription.
Point mutations.
Single nucleotide changes.
Name two substitutions.
Transition and transversion.
Transition.
Mutation causing changes from pyrimidine to pyrimidine (CT) or
Purine to purine (AG).
Transversion
Mutation causing changes from pyrimidine to purine or purine to pyrimidine.
What mutation results in frameshift?
Deletion or insertion (if not in groups of 3).
Inversion
Mutation in which order of block is reversed (break and rejoin).
Translocation.
Mutation in which part of a chromosome is moved into a new location (break and rejoin). e.g. Down syndrome - trisomy 21.
Synonymous mutation.
New codon codes for the same amino acid - no change in protein, e.g. ACT mutated to ACA - no change in amino acid, still thr.
Non-synonymous mutation.
New codon codes for a different amino acid - change in protein, for example, ACT change to GCT - amino acid change from thr to ala.
What do mutation in the somatic cell lead to?
Cancer.
Ames test.
Ames test is in vitro test to detect environmental mutagens.
How does radiation affect the body?
Radiation may cause single and double strand breaks in DNA. UV radiation - creates thymine dimers in DNA.
Name several mutation repair mechanisms.
- Proof-reading function of DNA polymerase corrects errors in DNA replication;
- Repair mechanisms to eliminate thymine dimers caused by UV radiation;
- Repair mechanisms can correct mispairing, but must be able to recognise which strand is wrong.