Describe the genetic factors associated with schizophrenia.

Key terms and concepts that may be included in student responses:
▪ Family studies-according to psychologist Irving Gottesman, children of two parents with schizophrenia and monozygotic twins of people with schizophrenia share the greatest number of genes with people with schizophrenia; as the genetic similarity to a person with schizophrenia decreases, an individual's risk of developing schizophrenia also decreases; having a biological relative with schizophrenia does not mean that the individual will develop it
▪ Adoption studies-when a parent is psychotic, the child may be exposed to illogical thought, mood swings, and chaotic behavior; Seymour Kety and colleagues found that the biological relatives of adoptees with schizophrenia were 10 times more likely to have a diagnosis of schizophrenia than were the biological relatives of adoptees who did not have schizophrenia; the adoptive relatives of adoptees with schizophrenia showed no increased risk for the disorder
▪ Twin studies-the concordance rate for monozygotic (MZ)twins is 46 percent, while the concordance rate for dizygotic (fraternal)twins is 14 percent; when a person carries a genetic risk for schizophrenia, many other biological and environmental factors may influence whether and how the disorder manifests itself; when MZ twins who were discordant for schizophrenia were compared with MZ twins who both had schizophrenia, researchers found that the MZ twins discordant for schizophrenia showed numerous differences in the molecular structure of their DNA; the MZ twins concordant for schizophrenia showed many fewer molecular differences in their DNA