In DM1, there is an expansion of the cytosine-thymine-guanine (CTG) triplet repeat in the DMPK gene. Between 5 and 37 repeats is considered normal, while individuals with between 38 and 49 repeats are considered to have a pre-mutation and are at risk of having children with further expanded repeats and, therefore, symptomatic disease.[9] Individuals with greater than 50 repeats are almost invariably symptomatic, with some noted exceptions. Longer repeats are usually associated with earlier onset and more severe disease.[citation needed]