Prof Marais speaks about his research into the genetic influence of the B-RAF mutation in melanoma. Using mice as models for the disease, Prof Marais' team have been working to identify the mechanism of action of different melanoma therapies and to test the specificity of different drugs. This research has revealed that drugs with tumour inhibiting effects in patients with the B-RAF mutation can lead to hyperactivity in patients with the RAS mutation and could promote tumour growth.