The HTR2A gene has been mapped to 13q14.2 chromosome; it encodes serotonin 5-HT2A receptors that are located primarily in the neocortex, caudate nucleus, nucleus accumbens, olfactory tubercle, hippocampus and vascular and non-vascular smooth muscle cells.  Serotonin is critical to so many processes in the central nervous system; 5-HT2A receptors play a role in appetite control, thermoregulation, sleep, and also involved, along with various other 5-HT receptor populations, in cardiovascular function and muscle contraction.  In addition, serotonin 5-HT2A functions as a receptor for various drugs and psychoactive substances, including mescaline, psilocybin, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and lysergic acid diethylamide (LSD).

The HTR2A gene comprises three coding exons, and spans greater than 65 kb.  The encoded protein, serotonin 5-HT2A receptors, is 471 amino acids in length and weighs 52.6 kDa.  HTR2A gene has multiple transcript variants encoding different isoforms.  Polymorphisms in this gene are believed to be associated with susceptibility to alcohol dependence, anorexia nervosa 1, major depressive disorder, obsessive-compulsive disorder, and schizophrenia.  Moreover, the HTR2A gene is an example of genes that are polymorphically imprinted. 

5-HT(2A) receptors could act as the cellular receptor for human polyomavirus (JCV) on human glial cells.  The latter virus causes the fatal demyelinating disease; progressive multifocal leukoencephalopathy in immunocompromised patients, therefore serotonin receptor antagonists were suggested for the treatment of this condition.