The LCT (lactase) and MCM6 (regulatory protein that control lactase production) genes are located on chromosome two, one of the autosomal chromosomes. Autosomal chromosomes are inherited in pairs – one from each parent.
If an individual inherits two copies of the wild type MCM6 gene, they will be lactose intolerant in adulthood and will pass this wild type gene to the next generation.
If an individual inherits two copies of a variant MCM6 gene, they will have lactase persistence and will pass this lactase persistence to the next generation.
If an individual has one copy of a wild type MCM6 gene and one copy of a variant MCM6 gene, they usually have lactase persistence (although there may be some lactose sensitivity). This pattern of inheritance is referred to as autosomal dominant as only one copy of the variant gene is required to provide the lactase persistence.