This is not the London Tube Map. Using a mating type approach with a two-locus model, we were able to translate odds ratios into the probability that an affected sibling also carries the risk variant. For some microdeletions with a low odds ratio, this probability is little more than the 50% expected by chance.

Ingo Helbig

Child Neurology Fellow and epilepsy genetics researcher at the Children’s Hospital of Philadelphia (CHOP), USA and Department of Neuropediatrics, Kiel, Germany