Is multiple sclerosis caused by a gene?

No: The cause of multiple sclerosis is unknown, there is some evidence that is related to a viral infection and there is evidence that genetics plays a part. However, there is no conclusive evidence that there is a single cause. In the end, we may find that "susceptible" individuals exposed to a trigger at the "right" age, with the right genetic profile go on to develop ms--thus a multifactorial cause.

Not the standard way: Ms is an autoimmune mediated disorder, which occurs in genetically susceptible folks, if appropriate environmental influences are present. It is not a traditional genetic disease whatsoever, but may occur in families who have similar susceptibility genes.

Unsure: It is not clear there is one gene involved in multiple sclerosis. there may be many genes, there may be factors associated with genes, such as methylation, a so-called epigenetic effect. There are several known factors in the cause of MS, but for the most part, it is best to say we do not know what the cause is.