As one learns from the passage, the current genetic studies of schizophrenia ----.

The causes of schizophrenia are unknown, although
the disease has a strong genetic component. Studies
of identical twins show that if one twin has
schizophrenia, there is a 50% chance that the other
twin will have it, too. Since identical twins share
identical genes, this indicates that schizophrenia has
an equally strong environmental component, the
nature of which has not been identified. Current
treatments for schizophrenia focus on brain
pathways that use dopamine as a neurotransmitter.
Despite their ability to alleviate symptoms, many of
the drugs used to treat schizophrenia have such
negative side effects that patients frequently stop
taking them. Now that the human genome has been
sequenced, there is a vigorous effort under way to
find the mutant genes that predispose a person to
the disease. This effort includes sequencing DNA
from families with a high incidence of schizophrenia.