But a defective ATM gene can interfere with p53 thereby allowing potentially cancerous cells to multiply.

BBC: Gene research

The research team believes if doctors can identify people who have the ATM gene fault, they can be targeted for screening and prevention.

BBC: Breast cancer gene discovered

The researchers found that around 20% of CLL tumours had a faulty ATM gene, and another 10-15% had an abnormality in the p53 gene.

BBC: Gene research

Scientists believe that patients with this mutant ATM gene may have a more aggressive form of CLL which is more difficult to treat with conventional drugs.

BBC: Gene research