Although many human disorders can be explained by simple Mendelian inheritance patterns, others are more complex in nature. Multifactorial diseases are influenced by a range of factors, including an individual's genetics and environment. An example of a complex illness is schizophrenia, a mental affliction caused by a chemical imbalance or irregular structure of the brain. Schizophrenia is characterized by hallucinations or delusions and prevents individuals from rationalizing, controlling their emotions, communicating, or making independent choices. Thus, schizophrenia is a complex and chronic disorder that affects individuals in unique ways and is influenced by both genetic and environmental stimuli (“What”). From a genetic perspective, scientists and researchers know that schizophrenia involves multiple chromosomes and occurs at a higher frequency in people. with a history of schizophrenia in their family. So far, loci suspected of correlating with higher susceptibility or with the disease itself have been located on all autosomal chromosomes, excluding chromosomes seven, nine and twenty-one, and one locus was found on the X sex chromosome (“Genes”). Some chromosomes even have several loci at which a link with schizophrenia has been established, but the exact cause of the disease still remains a mystery. On the other hand, the particular deletion of 22p11.2, a locus on chromosome twenty-two, offers interesting phenotypic observations associated with schizophrenics. 22p11.2 deletion syndrome has been observed in approximately 1% of the schizophrenia population, and people with the mutation appear to have the same symptoms and phenotype as other schizophrenics. However, it is known that people with 22pDS...... middle of paper ...... faulty connection between them often leads to neurological and psychological disorders. Studies have shown that changes in the brain between schizophrenics and non-schizophrenics occur primarily in the frontal cortex, the brain's processing center for rational thinking, explaining why schizophrenics struggle with delusions and processing logic ("Causes "). Works Cited Bassett, Annie S. “Schizophrenia and 22p11.2 deletion syndrome.” »NCBI. NP, 2008. Web. March 9. 2014. “Disease-associated genes.” » Genetic maps. Weizmann Institute of Science, 2014. Web. March 9. 2014. “L1 gene skipping involved in schizophrenia.” » Schizophrenia Research Forum. NP, 2014. Web. March 9. 2014. “The causes of schizophrenia.” National Alliance on Mental Illness. Np, and Web. March 9. 2014. “What is schizophrenia?” » National Alliance on Mental Illness. Np, 2013. PDF file.