Causes of mutation
A random and spontaneous change in the structure of a gene, chromosome or number of chromosomes. is a change in a The basic unit of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell's chemistry - particularly protein production. or The structure made of DNA that codes for all the characteristics of an organism.. It is a rare, random change in the genetic material and it can be inherited.
Mutation occurs continuously and can be spontaneous. It can also happen because of:
- Radiation that is able to remove electrons from atoms or molecules to produce positively charged particles called ions.
- chemical mutagens - such as tar from cigarette smoke
Ionising radiation includes gamma rays, X-rays and ultraviolet rays. The greater the dose of radiation a cell gets, the greater the chance of a mutation.
Mutations could cause different genes to be switched on or off, and this could create a different or faulty protein to be synthesised.
For example, if the protein is an important enzyme, the specific substrate might not fit into the substrate binding site. If it is a structural protein such as collagen, it might lose its strength.
However, most DNA mutations do not alter a protein, they only alter it slightly so its appearance or function is not changed.
There are many different types of mutations which can arise in DNA.
Image caption, Original gene structure
This shows the normal order of the bases for one of the strands. Only one of the strands of DNA is involved in protein synthesis. A change from the normal order of bases leads to different types of gene mutation. (eg CGA / ACT / CGA)
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These mutations may:
- change the activity of a protein in a coding part of the DNA
- or
- change how the genes are expressed if the change is in a non-coding section of DNA
These might result in phenotype changes or they might appear hidden, and be unnoticed. Alternatively, they might result in a serious consequence, for example, genetic disease such as cystic fibrosis.