Researchers have identified two new genes that double a person's risk of developing melanoma, the deadliest form of skin cancer.

Researchers from the Queensland Institute of Medical Research (QIMR) studied the genes and mole count of nearly 6,000 people.

They found that particular changes in two genes increased the subjects' risk of developing moles. The researchers then found in another 4,000 subjects that having those same two genes doubled melanoma risk.

Lead researcher Nick Hayward said the findings improve researchers' understanding of the genetic pathways that can lead to melanoma.

"It has long been known that having a large number of moles is the biggest risk factor (for melanoma)," Hayward said. "Therefore we predicted we would find genes linking moles and melanoma. We now have conclusive genetic evidence that having a large number of moles increases an individual's risk of developing melanoma."

The findings are published in the journal Nature Genetics.

While melanoma is the least common of the three types of skin cancer, it is also the most serious.

It begins in the melanocytes, which produce melanin to give colour to the skin. When skin is exposed to the sun, melanocytes produce more melanin, causing the skin to darken. Melanocytes can cluster together to form moles.

While having moles is normal, they must be watched for changes in shape, size, colour and texture.

The Canadian Cancer Society estimates that 5,000 new cases of melanoma will be diagnosed in Canada in 2009.

The new research also has implications for those who only carry one of the two genes. Those subjects have a 25 per cent increased chance of developing melanoma.

According to Hayward, the research will eventually aid in the development of better screening techniques and treatment for the disease.

In the meantime, patients with a large number of moles, who are at higher risk of developing melanoma, should avoid overexposure to ultraviolet radiation.