This penetrance of schizophrenia is long seen, you know, if your father is schizophrenic, you might think if it was a dominant gene you had a 50% chance of getting it. Yet the figure it's about 10% of a parent. And in identical twins where you know they have the same DNA, it's 50%. I think the problem is that if you asked if the people were slightly odd but not psychotic, not hospitalized, that the frequency of the twin having some problem might be 75%, but I can't speak with the assurance that I think - there's a weakness that you're subject to psychosis. And people don't really know whether - what aspect of mental illness might be associated with genetic changes where through methylation or other modification of the histones, reagents either become over-expressed or under-expressed. And looking at the - looking at brains that have been collected after the deaths of schizophrenic people, there seems to be an overabundance of expression of templates for a gene which is - does a lot of methylation. So - and one of the medicines taken to bring you out of mania is a histone deacetylase. So, you know, psychosis could be – an epigenetic change. So the gene may or might or might not make you schizophrenic depending on whether the epigenetic thing - and I think within five years, we'll move on from just sequencing the DNA but looking for methylation changes. The problem is that generally we just have blood from people with schizophrenia. You know, they're still living, we do not have a sample of their brain DNA. So schizophrenia in that sense will be harder to find the epigenetic changes which we know are behind some cancers. Then - so it's going to be a hard problem finding out why we have it, but you know, some people like to say because, you know, not every identical twin gets it, it's not genetic. But it's many more than, it's a much higher percentage than you would have by chance. So generally, the chance that if your brother is schizophrenic that you will be schizophrenic is again 10%, but identical twins is 50%. That doesn't quite add up to me. You know, I like sort of 20% and 50% or something like that. But there's something more than genes, but we think, you know, it's modification of genes, not just, you know, non-genetic changes to your brain.
