Schizophrenia is a psychotic disorder where the patient has a few, if not all, of the following major symptoms: withdrawl from reality, illogical thinking patterns, delusions and hallucinations (answers.com).
Just knowledge of the symptoms of a disease is not enough to create a cure or even settle a dispute about the reality of a disease. Especially when discussing mental illnesses, it is extremely important to find the pathology of a disease, which in most cases includes finding genetic links. There will always be those that dispute the legitimacy of mental illnesses, but by finding the genetic link to schizophrenia it has become harder for people to say that schizophrenia is not real.
It has been assumed for many years that schizophrenia has a genetic link due the studies done on identical twins with schizophrenia. The studies have found that a person is more than 50% likely to develop schizophrenia if their twin has it. Until recently the link has be simply been based on Mendel’s genetics. Scientists used Mendel's laws to ascertain the probability that a person would inherit the disease. Yet, that is not enough to truly understand the disease. Since schizophrenia is inherently hard to treat, knowledge of any genetic links will help scientists develop better treatments.
Scientists have recently found a gene that is associated with the onset of schizophrenia. On the chromosome 8p21.3 there is a gene called PPP3CC. The gene PPP3CC codes for a calcineurin gamma subunit. Calcineurin is in charge of dopamine signaling and has a role in the plasticity of the brain. Dopamine is a chemical that affects movement control, emotions, pleasure responses and pain responses. Plasticity refers to the brain's ability to adjust and reform connections after illness or trauma. Both dopamine and plasticity are issues in schizophrenia.
Scientists manipulated the gene, PPP3CC in knockout mice. Knockout mice are mice that have had their genes altered to display a desired characteristic. Mice are ideal for this process due to their short lifecycle as well as the fact that mice exhibit similar characteristics to human disease progression. In this case the scientists altered the PPP3CC gene in order to lower the levels of calcineurin and thus reduced the gene's signaling ability.
Mice are not ordinarily susceptible to schizophrenia which created a built in control group for the experiment. A control group is a group that is not exposed to the variable, which in this case is the altered gene. The knockout mice exhibited poor working memory and social withdrawal. When given a diagnostic test for schizophrenia that uses loud noises, the mice responded similarly to the test as patients with schizophrenia did. Another unusual behavior was that the mice scattered their nesting around their cage. Drugs that work for schizophrenia patients also worked for the mice.
My sources for this information are:
Demars, Sandra. Evidence for assocation of schizophrenia with genetic variation in the 8p21.3 gene, PPP3CC,
encoding the calcineurin gamma subunit. Susumu Tonegawa. May 15 2003
Also, some of the more generic information was acquired in general psychology classes.