Mutations

• Mutagens


  • radiation - e.g. UV light and x-rays
  • chemicals
  • infectious agents - viruses can insert themselves into the genome
• Mutagens


  Increase the chance of a change within the DNA
• Mutation


  any change to the base sequence
• Mutations can be beneficial with advantageous effects

  Antibiotic resistance in bacteria increases their chance of survival
• Mutations can be harmful with disadvantageous effects

  Cystic fibrosis as excess mucous is produced as the CTFR protein folds incorrectly due to mutation
• Mutations can have a neutral effect

  • same amino acid has been coded for
  • if a different amino acid has been coded for, it may have a similar chemical property as the right amino acid
  • amino acid may be an intron
  • amino acid may not be involved in structure
• Point mutations are the changing of one base directly

  • insertion
  • deletion
  • substitution
• Insertion and deletion


  • results in a frame shift
  • this causes the polypeptide that is created to be completely wrong
• Substitution: non-sense mutation


  • premature stop codon is coded for
  • e.g. thalassemia - anaemia
• Substitution: mis-sense mutation


  • different amino acid is coded for
  • e.g. sickle cell disease
• Substitution: silent mutation


  • due to degenerate nature of genetic code
  • different bases coded, results in the same amino acid
  • no change overall