alteration of the sequence of bases in DNA

• gene mutations:

  alteration of base sequences

  occurs in DNA replication

  chances can increase due to mutagenic agents 

  (carcinogens + high energy ionising radiation)
• what does gene mutations result to

  different amino acid sequences

  • modifies tertiary structure (hydrogen and ionic bonds)

  leads to a non-functioning protein
• addition mutation

  DNA nucleotide is added to the sequence

  causes a frame shift

  codes for different amino acids
• deletion mutation

  DNA nucleotide is deleted from the sequence

  causes a frameshift - triplets would be different
• substitution mutation

  one base is different

  not as harmful - only one codon would differ

  degenerate (genetic code) - could still coe for the same amino acid
• inversion mutation

  section of bases are inverted

  • results to different amino acids
• duplication mutation

  one or more bases are duplicated in the base sequence, leading to frame shift
• translocation mutation

  section of bases on a chromosome breaks off and attaches to a different chromosome

  • leads to abnormal phenotypes