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This goes into more detail about the genetic mutation responsible for Gilbert's Syndrome. Genetic mutations are given a asterisk notation, and the mutation causing Gilbert's Syndrome is called UGT1A1*28. The mutation is not in the structure of the enzyme, which is fine, but in the amount of it that is produced. The area responsible for this is called the promoter region. In Caucasian and African populations, this is the most common cause of Gilbert's Syndrome, while in Japanese populations, a mutation known as G71R alters the effectiveness of the UGT1A1 enzyme with nearly identical results.