Eytan has been diagnosed with schizophrenia. What is the risk that his identical twin, who grew up in a different family, also has schizophrenia?
1) The risk is slightly higher than in the general population because they are twins, but grew up in a different environment.
2) The probability is close to 50 percent because there is a genetic predisposition to schizophrenia, but they grew up in a different environment.
3) The probability is 100 percent because they share the same genetic material, and the environment does not have an influence.
4) The risk is the same as for any individual in the population because schizophrenia is not heritable.