Mutations

• Sometimes the sequence of DNA bases can be changed. These changes are called mutations
• Mutations are changes to the genetic code
• Occasionally a gene may mutate. A mutation is a random change in an organism's DNA. They can sometimes be inherited
• Mutations occur continuously. They can occur spontaneously, e.g. when a chromosome isn't quite replicated properly
• The chance of mutation is increased by exposure to certain substances or some types of radiation
• Mutations change the sequence of the DNA bases in a gene, which produces a genetic variant. As the sequence of DNA bases codes for the sequence of amino acids that make up a protein, mutations to a gene sometimes lead to changes in the protein that it codes for
• Most mutations have very little or no effect on the protein. Some will change it to such a small extent that its function or appearance is unaffected
• Some mutations can seriously affect a protein. Sometimes, the mutation will code for an altered protein with a change in its shape. This could affect its ability to perform its function
• If the shape of an enzyme's active site is changed, its substrate may no longer be able to bind to it
• Strutural proteins like collagen could lose their strength if their shape is changed, making them pretty useless at providing structure and support
• If there's a mutation in the non-coding DNA, it can alter how genes are expressed
• There are different types of mutation: Insertions, deletions and substitutions
• Deletions

  • Deletions are when a random base is deleted from the DNA base sequence
  • Like insertions, they change the way that the base sequence is 'read' and have knock-on effects further down the sequence
• Substitutions

  • Substitution mutations are when a random base in the DNA base sequence is changed to a different base

  
• Insertions

  • Insertions are where a new base is inserted into the DNA base sequence where it shouldn't be
  • Every 3 bases in a DNA base sequence codes for a particular amino acid
  • An insertion changes the way the groups of 3 bases are 'read', which can change the amino acids that they code for
  • Insertions can change more than one amino acid as they have a knock-on effect on the bases further on in the sequence