Model answer: Describing the role of genes in schizophrenia

This explanation of schizophrenia suggests that a predisposition to developing schizophrenia is heritable, meaning that it can be passed from parent to offspring via genes, which are the units of heredity which determine certain biological characteristics.

Genes are carried on chromosomes and research has suggested that there are as many as 700 genes which are linked to schizophrenia; so far 13 chromosomes have been linked to schizophrenia but much interest revolves around chromosomes 13 and 6.

Genes, such as COMT and DISC1, which responsible for the regulation of neurochemicals such as dopamine and GABA are most commonly linked to schizophrenia.

For example, deletion of a specific part of chromosome 22, containing around 30-40 genes, causes DiGeorge syndrome where as many as 1 in 4 people with the condition develop schizophrenia; this may be because this region houses the ‘COMT’ gene which codes for the enzyme (catechol-O-methyltransferase) which breaks down dopamine. Deletion of this gene could, therefore, lead to hyperdopaminergia and potentially cause positive symptoms such as hallucinations and delusions.

Similarly, people with an abnormality to the DISC1 gene, which regulates levels of GABA, are also more likely to develop schizophrenia than people without this abnormality; the interaction between glutamate, GABA and dopamine in regions such as the limbic system have also been linked to the development of schizophrenia.