What types of mutation are there?

There are lots of different mutations that can occur in our DNA. 

Small-scale mutations

  • Substitution – when one or more bases in the sequence is replaced by the same number of bases (for example, a cytosine substituted for an adenine).
  • Inversion – when a segment of a chromosome is reversed end to end.
  • Insertion – when a base is added to the sequence.
  • Deletion – when a base is deleted from the sequence.

Large-scale mutations

  • Copy number variation (CNV) is a type of mutation where large chunks of DNA are inserted, repeated or lost. These regions of DNA can be between 10,000 and 5,000,000 bases long.
  • Duplication of genes. When there is an increase in the number of copies of a gene.
  • Deletions of large regions of the chromosome.
  • Loss of one copy of a gene in an organism that previously had two copies.
  • Loss of both copies of the same gene.
  • Movement of sections of DNA from one location to another.
  • Addition of an extra copy of a chromosome. For example, an extra copy/partial copy of chromosome 21 results in Down’s syndrome.

How do we inherit mutations?

  • Each of our genes is a copy from either our mum or our dad. If there is a mutation in one of these genes, this can be passed on from parent to child along with the rest of their genes.
  • Small inherited changes can make big differences to our bodies. For example, the most common mutation to cause cystic fibrosis is the loss of three letters in a gene called CFTR
  • Even though mutation is common, inherited diseases are relatively rare. This is because inherited diseases are often recessive, which means that a person must have two copies of the mutated gene to get the disease. 

Image credits: Genome Research Limited

This page was last updated on 2021-07-21