The cause of Batten disease lies in the chromosomes, which carry the hereditary characteristics and are found in the nuclei of somatic cells. The nucleaus of every cell in the body contains twenty-three pairs of chromosomes. Each gene represents the 'code' for a particular characteristic. In the case of Batten disease, there is an aberration in one of the genes in one pair of chromosomes.
RECESSIVE MODE OF INHERITANCE
B b B b
B B B b B b b b
Normal Carriers Affected
Childhood NCLs are autosomal recessive disorders; that is, they occur when a child inherits two copies of the defective gene, one from each parent. When this occurs, each of their children has a one in four chance of developing NCL or a one in two chance of inheriting just one copy of the defective gene. Individuals who have only one defective gene are known as carriers, meaning they do not develop the disease, but they can pass the gene onto their own children.
Although there is no conclusive test yet available to identify carriers of the affected gene, recent breakthroughs in identification of the infantile and juvenile types have brought this one step closer.
Adult NCL may be inherited as an autosomal recessive or, less often, as an autosomal dominant disorder. In autosomal dominant inheritance, all people who inherent a single copy of the disease gene develop the disease. As a result, there are no unaffected carriers of the gene.