mutations

• Silent


  .One DNA base (A,T,C or G) is substituted for another

  .The triplet base codon will code for the same amino acid despite the change

  .Degenerate- A single amino acid may be coded for by more than one codon
• Indel


  .Insertion or deletion of a nucleotide + base

  .Changes every codon from then on to code for a different amino acid and form different proteins

  .This is called frameshift

  .Can be harmful
• Missense


  .One DNA base is substituted for another

  .Triplet base codon will code for a different amino acid

  .May have no effect on the overall protein or render it faulty
• Nonsense


  .One DNA base is substituted for another

  .Forms a stop-codon which does not code for an amino acid at all

  .Causes a shortened protein chain that may or may not work
• Mutagenic agents 


  . High energy ionising radiation- alpha, Beta, X-rays, UV

  . Carcinogens-.Smoke, mustard gas, peroxides, interfere with DNA structure or transcription