Montrose Q: Why are identical twins more disposed to have problems? Are both twins equally disposed and if not, why?
Sorry for the confusion. Identical twins share all the same genes; fraternal twins share about half, like any other siblings. We want to know if there is a genetic component to schizophrenia. We ask one of each pair of 100 identical twins, and one of each pair of 100 fraternal twins, if they are schizophrenic. 10 in each group say yes. Then we ask them about their sibling. We find that only one of the fraternal twins siblings is also schizophrenic, but 6 of out 10 identical twins with schizophrenia also has a twin with schizophrenia. This would indicate that there is a strong genetic component to the disease. It’s one of the reasons we study mice so much: inbred mice are all like identical twins, and if you find such a strain that in which all have, say, lupus, you know it’s a genetic disease and can begin to unravel the genes involved.
