RG Mutations

• What are mutations?

  Changes to the base sequence of DNA
• What do gene mutations involve?

  A change in the DNA base sequence of chromosomes
• What types of errors that can occur include?

  • Substitution
  • Deletion
  • Insertion
  • addition
• Describe substitution?


  One base is substituted with another (eg ATG becomes ATT)
• Describe deletion?

  One base is deleted (eg ATGCCT becomes ATCCT)
• What does the order of DNA bases in a gene determine?

  The order of amino acids in a particular protein
• What could happen if a mutation occurs in a gene?

  The sequence of amino acids it codes for, and the protein formed, could be altered
• Why will not all substitution mutations result in a change to the amino acid sequence of the protein?

  The degenerate nature of the genetic code = some amino acids are coded for by more than one DNA triplet

  = not all substitution mutations will result in a change to the amino acid sequence of the protein -

  some substitutions will still code for the same amino acid
• What type of mutations will always lead to changes in the amino acid seq?

  deletions
• What will deletions always lead to?

  Changes in the amino acid sequence
• Why do deletions ALWAYS lead to changes in the amino acid seq?

  The deletion of a base will change the number of bases present, which will cause a shift in all the base triplets after it
• What increase the rate of mutation?

  Mutagenic agents
• When do mutations occur?

  spontaneously eg when DNA is misread during replication
• What things can increase the rate of mutations?

  MUTAGENIC AGENTS
• Give examples of mutagenic agents?

  • Ultraviolet radiation
  • Ionising radiation
  • Some chemicals and some viruses