Final answer:
In humans, SNPs associated with lactase persistence are found in the regulatory regions of the LCT gene, which is responsible for the production of the enzyme lactase.
Step-by-step explanation:
The SNPs (single nucleotide polymorphisms) associated with lactase persistence are not located within the genes described here such as the lacZ, lacY or lacA genes, which are related to lactose metabolism in E. coli. Instead, in humans, variations associated with lactase persistence, which is the ongoing ability to digest lactose into adulthood, are typically found in the regulatory regions upstream of the LCT gene (lactase gene). The LCT gene is responsible for the production of the enzyme lactase in humans. Intolerance to lactose in humans usually results from a decrease in the expression of the LCT gene after weaning, leading to lactase non-persistence. However, certain SNPs can lead to continued expression of LCT, resulting in what is known as lactase persistence.