By Kyra Mandas and Stephanie Watkins
One of the most current, supported theories is a genetic etiology of autism. In 2008, Volker and Lopata discovered that, when studying twins with autism, monozygotic twins have a 60% co-occurrence rate and siblings have a 4% co-occurrence rate. These are both higher than the general population which is only .1%-.16%. Currently, scientists are using genome-wide scans to look at linkages in the chromosomes that relate to the occurrence of autism(Volker & Lopata, 2008). Volker and Lopata agree with Kabot, Masi, and Segal (2003) have found that chromosomes 15 and 7 have shown a relationship to the diagnosis of autism. Chromosome 15 malformations are the most common genetic malformations seen in autism cases (Volker & Lopata, 2008). This chromosomal area is also associated with epilepsy that has a high prevalence in children with autism. There has not been a specific gene on chromosome 7 that has been correlated with autism but there has continuously been malformation in that area in autism cases (Volker & Lopata 2008). Kabot, et al.(2003) mention in their article, Advances in the Diagnosis and Treatment of Autism Spectrum Disorder, that if these chromosome abnormalities are not the causes of autism they at least make a person more susceptible to the disease (Kabot, et al. 2003).
While it is important to remember that no specific chromosome has been associated with autism, recent developments in genetic screening have allowed researchers to investigate chromosomal abnormalities reported in association with autism spectrum disorders. Single gene defects, such as Fragile-X Syndrome and Rett syndrome account for approximately 20% of individuals with autism, but the origin of the disorder is unknown in the remaining 80% of individuals (Lo-Castro, Benvenuto, Galasso, Profirio, & Curato, 2010). It is hypothesized that the combination of particular microdeletions, microduplications, as well as other genetic mutations, may lead to autism spectrum disorder.
Examples of abnormalities in particular chromosomal regions are 2q37 (proteins in membranes, axon guidance, and cell proliferation), 17p11.2 (postnatal development and neuronal differentiation), and 22q11.2 (defenses against oxidative stress and neurotransmitter release) (Lo-Castro et al., 2010).
Kabot, S., Masi, W., & Segal, M. (2003). Advances in the diagnosis and treatment of autism spectrum disorders. Professional Psychology: Research and Practice, 34(1), 26-33. doi:10.1037/0735-7028.34.1.26
Lo-Castro, A., Benvenuto, A., Galasso, C., Porfirio, C., & Curatolo, P. (2010). Autism spectrum disorders associated with chromosomal abnormalities. Research in Autism Spectrum Disorders, 4, 319-327.
Volker, M.A., & Lopata, C. (2008). Autism: A review of biological bases, assessment, and intervention. School Psychology Quarterly, 23(2), 258-270. doi: 10.1037/1045-38220.127.116.118
Emory Photography & video (2009, April 16). Genetics of autism . Retrieved from http://www.youtube.com/watch?v=TLeB420k3zs
Diagram of Chromosomal Abnormalities: Lo-Castro, A., Benvenuto, A., Galasso, C., Porfirio, C., & Curatolo, P. (2010). Autism spectrum disorders associated with chromosomal abnormalities. Research in Autism Spectrum Disorders, 4, 319-327.