Genes carry instructions for making proteins. Proteins are like building blocks that make up all the components of a cell. Generally, a person carries two copies of each gene - one copy inherited from our father and the second copy from our mother.
Batten disease is caused by defects (known as mutations) in 'CLN' genes. A person carrying one defective CLN gene is NOT affected by Batten disease. Known as a 'carrier', this person can pass the defective gene onto their children. A child will have Batten disease if it inherits TWO defective copies of a CLN gene - one from each parent, as illustrated here.
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