Scientists have identified a chemical in the body which could play a significant role in reducing susceptibility to serious diseases such as haemophilia, cystic fibrosis and cancer.

The enzyme, called MBD4, corrects gene mutations in humans.

Humans are complicated chemical machines

Professor Alan Clarke

Tests in the laboratory have shown that mice which lack the chemical are up to three times more likely to have gene mutations.

The research has been carried out by scientists at Cardiff University and the University of Edinburgh.

Gene mutations can be caused by environmental factors such as cigarette smoke or sunlight.

However, they can also be an unwanted side effect of the risky natural chemistry that goes on in the cells of our bodies.

Certain mutations can prevent genes from doing their jobs properly, and can lead to diseases such as cancer.

Gene shutdown

The shutting down of genes to prevent them over-producing is the process that carries the greatest risk of causing a mutation.

Gene shutdown is achieved by marking them with chemical switches called methyl-groups.

It is thought that as many as one in three disease-causing genetic mutations is the result of a fault in this process.

No amount of care in avoiding harmful agents in food or air can escape this problem, which goes with being alive.

The researchers have discovered that the MBD4 enzyme tries to repair the damage caused by methyl-groups before it can do harm.

'Key defence'

Researcher Professor Alan Clarke said: "It is very likely the MBD4 is a key defence against self-inflicted gene damage in humans.

"Humans are complicated chemical machines, and we have evolved to use certain chemical tricks to control gene expression - which unfortunately have a significant down side in terms of gene damage.

"As humans we therefore had to invent a tool kit to repair the damage, and what we show here is that loss of part of that tool kit can increase the risk of developing cancer."

The research is published in the journal Science.