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OCR A Biology

Base Dna Mutagens Mutations Physical Biological Agents Sequence

Front 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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