OCR A Biology
Base Dna Mutagens Mutations Physical Biological Agents Sequence
Mutations can occur spontaneously or be induced by mutagens like radiation and chemicals; damage to DNA bases like depurination or oxidation by free radicals can also cause mutations, which antioxidants can help prevent.
Mutations can arise spontaneously or be induced by mutagens (physical, chemical, or biological agents). Depurination, depyrimidination, and free radicals can also cause mutations, which can be counteracted by antioxidants.
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Causes of mutations |
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- spontaneous, rate of mutations increased by mutagens (chemical, physical or biological agent causing mutations)
- physical mutagens - radiation which breaks DNA strands (one or both)
- chemical mutagens - deaminating agents - alter DNA bases e.g C to U, changing base sequence
- biological agents - viruses which insert itself into genome, altering base sequence
- depurination (loss of purine base) and depyramidination (loss of pyramidine base) random, and absence leads to insertion of incorrect base via complimentary base pairing in DNA replication
- free radicals (oxidising agents) affect nucleotide structure and distrupt base pairing during DNA replication, antioxidants (e.g vitamins) are anticarcinogens as they negate effects of free radicals
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OCR A Biology