URL of this page: https://medlineplus.gov/genetics/gene/mcm6/

MCM6 gene

minichromosome maintenance complex component 6

Normal Function

The MCM6 gene provides instructions for making 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 other dairy products. Lactose intolerance in adulthood is caused by gradually decreasing expression of the LCT gene after infancy, which occurs in most humans.

At least four variations have been identified in the regulatory element that modulates LCT gene expression. These variations change single DNA building blocks (nucleotides) in the regulatory element. Each of the variations 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.

More About This Health Condition

Other Names for This Gene

  • DNA replication licensing factor MCM6
  • MCG40308
  • MCM6 minichromosome maintenance deficient 6 (MIS5 homolog, S. pombe)
  • minichromosome maintenance deficient (mis5, S. pombe) 6
  • minichromosome maintenance deficient 6 homolog
  • Mis5
  • MIS5 homolog
  • P105MCM

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases


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  • Jarvela IE. Molecular genetics of adult-type hypolactasia. Ann Med. 2005;37(3):179-85. doi: 10.1080/07853890510007359. Citation on PubMed
  • Olds LC, Sibley E. Lactase persistence DNA variant enhances lactase promoter activity in vitro: functional role as a cis regulatory element. Hum Mol Genet. 2003 Sep 15;12(18):2333-40. doi: 10.1093/hmg/ddg244. Epub 2003 Jul 22. Citation on PubMed
  • Robayo-Torres CC, Nichols BL. Molecular differentiation of congenital lactase deficiency from adult-type hypolactasia. Nutr Rev. 2007 Feb;65(2):95-8. doi: 10.1111/j.1753-4887.2007.tb00286.x. Citation on PubMed

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