A gene is a piece of biological information you inherit from your parents. It is present in every cell of the body and tells cells what to do. Genes control cells by producing proteins; each gene is really a kind of recipe for making a certain protein.
Genes are usually attached to a chromosome (a strand of DNA containing many different genes). Each human cell contains around 25,000 genes and most have 23 pairs of chromosomes.
The Huntington’s gene - the gene that determines whether you will develop Huntington’s disease - is attached to chromosome pair number 4.
You can find out if you carry the faulty gene by taking a blood test known as a predictive test. You need to be 18 years old to take the test.