What is the genetic cause of Tourette's Syndrome?

I need to research this for a summer assignment. All I need to know is whether it's caused by a chromosomal abnormality or a dysfunctional gene. And it would be a great help if you also posted where you got your information. Thanks!

The cause has not been established, although current research presents considerable evidence that the disorder stems from the abnormal activity of at least one brain chemical (neurotransmitter) called dopamine. There may be abnormal activity of the receptor for this chemical as well. Undoubtedly, other neurotransmitters, e.g. serotonin, may involved as well.

Genetic studies indicate that TS is inherited as a dominant gene (or genes) causing different symptoms in different family members. A person with TS has about a 50% chance of passing the gene to one of his/her children with each separate pregnancy. However, that genetic predisposition may express itself as TS, as a milder tic disorder or as obsessive compulsive symptoms with no tics at all. It is known that a higher than normal incidence of milder tic disorders and obsessive compulsive behaviors occur in the families of TS patients.

The sex of the offspring also influences the expression of the gene. The chance that the gene-carrying child of a person with TS will have symptoms is at least three to four times higher for a son than for a daughter. Yet only about 10% of the children who inherit the gene will have symptoms severe enough to ever require medical attention. In some cases TS may not be inherited, and cases such as these are identified as sporadic TS. The cause in these instances is unknown.

There is a help group for this. Have you looked for it on google?

Genetic studies have proven that the overwhelming majority of cases of Tourette syndrome are inherited, although the exact mode of inheritance is not yet known.[3] Tic disorders have long been thought to be inherited as an autosomal dominant gene, but recent research challenges the autosomal dominant hypothesis, and suggests an additive model involving multiple genes.[4][5] According to Roger Freeman, M.D., "Genes that cause tics have not yet been identified; it's very unlikely there's just one. Tics are very familial, but not in a Mendelian pattern (dominant, recessive, etc.). You can't 'inherit' the committee decision to define a problem in a specific way, so TS can't itself be inherited. It's a tic disorder that is inherited." [6]

In some cases, tics may not be inherited; these cases are identified as "sporadic" Tourette syndrome (also known as tourettism) because a genetic link is missing.[7]

A person with Tourette syndrome has about a 50% chance of passing the gene(s) to one of his/her children. Gender appears to have a role in the expression of the genetic vulnerability, with males more likely to express tics than females.[4] Tourette syndrome is a condition of incomplete penetrance, meaning not everyone who inherits the genetic vulnerability will show symptoms. Tourette's also shows variable expression 鈥?even family members with the same genetic makeup may show different levels of symptom severity. The gene(s) may express as Tourette syndrome, as a milder tic disorder (transient or chronic tics), or as obsessive compulsive symptoms with no tics at all. Only a minority of the children who inherit the gene(s) will have symptoms severe enough to require medical attention.[8] There is currently no way to predict the symptoms a child may display, even if the gene(s) are inherited.

Recent research suggests that a small number of Tourette syndrome cases may be caused by a defect on chromosome 13 of gene SLITRK1. Some cases of tourettism (tics due to reasons other than inherited Tourette's syndrome) can be caused by mutation.[7] The finding of a chromosomal abnormality appears to apply to a very small minority of cases (1 - 2%). Studies to locate all of the genes implicated in Tourette's syndrome are ongoing.[9]

Also suggest checking PubMed for academic citations to further elaborate in detail.

Recent research suggests that it is a dysfunctional gene. Check out the study by Dr. Matthew State, Harvard.

I have the press release and the paper titled "Sequence Variants in SLTRK1 Are Associated With Tourettes Syndrome" in my computer. I can email them to you if you like.