Lactose intolerance is a recessive trait, whereas lactase persistence is dominant. Some changes in the MCM6 gene promote lactase production (lactase persistence). These changes are considered autosomal dominant, which means one copy of the altered gene is enough to sustain lactase production. People who do not have even one copy of the altered gene may show lactose intolerance symptoms to some extent.
The type of lactose intolerance that occurs in infants (congenital lactase deficiency) is caused by errors in the LCT gene. It follows an autosomal recessive pattern - this means that congenital lactase deficiency occurs only when an individual has two faulty copies of the LCT gene.
You can learn more about lactose intolerance here.