In terms of the clinical features of SCA8 we have found that it is a slowly progressive disease that affects the cerebellum, much more than it affects the brain stem or the cerebral hemispheres. Unaffected carriers do not show even subtle signs of the disease. Even though they have an abnormal copy of the gene, it is not enough to produce ataxia. Furthermore, we have been able to identify more that 20 other families that carry the gene responsible for SCA8 and the clinical features that we have identified in the large family are seen in these other families as well, though there are some interesting genetic differences. Dr. Ranum Speaks Molecular Features of SCA8 Chromosomes have many thousands of genes.
Genes can be thought of as sets of instructions, there are many genes on a chromosome.
The letters of the genetic code, the A's, C's, G's and T's, can be thought of as the alphabet that is used to write the set of instructions. Given this trend in ataxia genes of triplet repeat expansions in families with variable ages of onset and disease severity, we decided to develop a faster way to find expanded ataxia genes. The rapid cloning method allows us identify candidate genes much more quickly without depending on a large family to map that gene first because we don't need to know where the gene is located before we find it. We developed this method to isolate the SCA5 gene, but as fate would have it, SCA5 does not seem to be caused by a CAG expansion, so our method has not worked for SCA5. If SCA5 is caused by a repeat expansion it might be a different kind, a different sequence, or it may be a real short repeat that we cannot pick up with our method.