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MCM6 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

MCM6 gene

The MCM6 gene provides instructions for creating a protein essential for DNA replication and plays a critical role in regulating the body's ability to digest lactose.

Normal Function

The MCM6 gene provides instructions for making a protein that is part of the MCM complex, a group of proteins that functions as a helicase. Helicases attach to particular regions of DNA and temporarily unwind the two spiral strands of these molecules. When a cell prepares to divide to form two cells, helicases unwind the DNA so that it can be copied. The DNA that makes up the chromosomes is duplicated (replicated) so that each new cell will get a complete set of chromosomes. Helicases are also involved in the production of RNA, a chemical cousin of DNA.

Health Conditions Related to Genetic Changes

Lactose intolerance

A specific DNA sequence within the MCM6 gene called a regulatory element helps control the activity (expression) of a nearby gene called LCT. The LCT gene provides instructions for making an enzyme called lactase. This enzyme helps to digest lactose, a sugar found in milk and several other dairy products. Lactose intolerance in adulthood is caused by the gradually decreasing expression of the LCT gene after infancy, which occurs in most humans.

A few variants (also called mutations) have been identified in the regulatory element of MCM6 that controls LCT gene expression. These variants change single DNA building blocks (nucleotides) in the regulatory element. Each of the variants results in sustained lactase production in the small intestine and the ability to digest lactose throughout life. People without these changes have a reduced ability to digest lactose as they get older, resulting in the signs and symptoms of lactose intolerance.

Other Names for This Gene

  • MCM6_HUMAN
  • minichromosome maintenance deficient 6

Frequently Asked Questions

The MCM6 gene contains a regulatory element that controls the expression of the LCT gene, which produces the lactase enzyme. Specific variants in this MCM6 regulatory element allow for sustained production of lactase into adulthood, enabling the digestion of lactose. Without these specific variants, lactase production typically decreases after infancy, leading to lactose intolerance and digestive symptoms when consuming dairy.
Yes, genetic testing can identify specific single nucleotide variants in the MCM6 regulatory region associated with lactase persistence. However, it is important to note that lactose tolerance is polygenic and influenced by other factors, so a positive test for the MCM6 variant is a strong indicator but not a guarantee of complete tolerance. Many clinicians recommend a gradual reintroduction of dairy to assess individual tolerance rather than relying solely on genetic results.
Having the MCM6 variant indicates that your body continues to produce lactase, which significantly reduces the risk of typical lactose intolerance symptoms like bloating and gas. However, individual tolerance levels vary. Some individuals with the variant may still experience mild discomfort with very large quantities of dairy due to other digestive factors or specific sensitivities to milk proteins, so it is best to monitor your body's response.
The primary clinical relevance of the MCM6 gene in human health is its role in regulating lactase expression. While the MCM6 protein itself is essential for DNA replication as part of the MCM complex, the specific genetic variants discussed in clinical contexts are linked to lactose tolerance. There is no established direct link between common MCM6 variants and other major hereditary diseases or cancer syndromes.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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