Mutations

A mutation is a random change in the order of bases in a DNA sequence. Mutations occur continuously and they can cause changes in the protein that the gene codes for. Usually, a mutation will not change the appearance or function of the protein, because the change is very small.

Type of Mutations

There are different types of mutations that can occur in DNA:

  • Insertion
  • Deletion
  • Substitution
  • Inversion
  • Duplication

Insertion

A change in the DNA sequence caused by adding a new base or several bases into the DNA sequence. Every group of three bases codes for an amino acid. So, even if one base was inserted, it will have a knock-on effect because it will change the groups of three bases. This may result in a different protein being synthesised.

Deletion

A change in a DNA sequence caused by deleting a base or several bases from the DNA sequence. Even if one base was deleted, it will have a knock-on effect because it will change the groups of three bases. So, this may result in a different protein being synthesised.

Substitution

A change in a DNA sequence caused by swapping one or more bases in the sequence by the same number of bases. This will not have a knock-on effect, as it will only change the amino acid for one group of three bases.

Inversion

A piece of DNA is flipped 180 degrees and reinserted into the chromosome.

Duplication

A piece of DNA is duplicated, which results in multiple copies of that piece of DNA.

Coding DNA

The coding DNA is a sequence of DNA that codes for a protein.

Each gene contains different sequence of bases which code for a specific protein. So, if the order of these bases change, it can affect the shape of a protein.

Non-Coding DNA

DNA also carries sections of non-coding regions that don’t code for any amino acids but play a role in protein synthesis. Some non-coding DNA sequences can control the genes by switching them on and off.

So, a change in the order of bases in the non-coding regions of DNA can affect the way genes are expressed.