MCM6 rs4988236: Understanding Lactase Persistence Genetics
The rs4988236 variant is a genetic marker located within the MCM6 gene that is associated with the trait of lactase persistence. This trait allows individuals to continue producing the enzyme lactase, which is necessary to digest lactose, the primary sugar found in milk, into adulthood.
What each genotype means
Likely lactose intolerant
You carry two copies of the ancestral C allele, which is associated with adult lactase non-persistence. In many individuals with this genotype, intestinal lactase enzyme expression naturally declines after early childhood, often leading to digestive discomfort when consuming lactose-containing dairy products. However, symptom severity can vary widely depending on personal microbiome composition and total dietary lactose intake.
Carried by approximately 5% to 20% of people of Northern European ancestry, but predominates globally, occurring in over 70% to 90% of individuals across East Asian, African, and Indigenous American populations.
Likely lactose tolerant
You carry one copy of the lactase persistence T allele (historically designated -13910*T) and one ancestral C allele. Although enzyme activity levels are biologically intermediate compared to homozygotes, a single persistent allele is generally sufficient to sustain adult lactase production and digest dairy without symptoms. Lactase persistence operates as a dominant trait in European-derived populations, though tolerance may still depend on other genetic and gastrointestinal factors.
Carried by roughly 30% to 50% of individuals of European descent, but found at much lower frequencies in populations lacking pastoralist European admixture.
Lactase persistent adult
You carry two copies of the lactase persistence T allele in the regulatory region of the LCT gene. Research shows this genotype strongly correlates with sustained lactase enzyme production across adulthood and normal dairy digestion. While this variant strongly predicts lactose tolerance in European ancestry groups, independent regulatory variants influence lactase persistence in pastoralist populations of African or Middle Eastern descent.
Found in up to 40% to 70% of people of Northern and Northwestern European ancestry, but is rare or absent in populations of East Asian and unadmixed African ancestry.
What is rs4988236 and Where is it Located?
The rs4988236 variant is a single nucleotide polymorphism (SNP) situated on chromosome 2q21. Specifically, it is located within the 13th intron of the MCM6 gene. While the MCM6 gene itself is involved in DNA replication, this specific region acts as a regulatory enhancer for the neighboring LCT gene. The LCT gene is responsible for producing the enzyme lactase, which breaks down lactose in the small intestine. Because rs4988236 sits within a regulatory element, it does not change the structure of the MCM6 protein, but rather influences how the nearby LCT gene is expressed. This variant is one of several identified in the MCM6 region that are linked to the ability to digest milk sugars after childhood, a trait that varies significantly across different human populations globally.
The Role of the MCM6 Gene
The MCM6 gene encodes a protein that functions as part of the DNA replication licensing complex, which is essential for cell division. However, in the context of lactose digestion, the gene serves a secondary, distinct purpose as a host for regulatory sequences. Research has shown that the 13th intron of MCM6 contains critical enhancer elements that control the activity of the LCT gene promoter. In most mammals, the expression of the LCT gene is naturally downregulated after weaning, leading to a decrease in lactase production. Certain variants within the MCM6 enhancer region, including those linked to rs4988236, can prevent this downregulation. By maintaining higher levels of lactase mRNA and enzyme activity in the intestinal lining, these regulatory variants allow for the continued digestion of lactose throughout an individual's adult life.
Research and Evidence Strength
The association between variants in the MCM6 intron 13 region and lactase persistence is well-documented in scientific literature. While rs4988236 is specifically noted in studies of certain populations, such as those in East Asia, it is part of a broader group of over twenty SNPs in the MCM6 region that have been linked to the lactase persistence trait. The evidence for these variants acting as cis-regulatory elements is strong, supported by functional studies in intestinal cell cultures showing that these sequences enhance promoter activity. However, the strength of the association for any single variant can be highly ancestry-specific. Because lactase persistence evolved independently in different human groups, the specific genetic marker responsible for the trait in one population may not be the same as in another. Therefore, while the biological mechanism is clear, the predictive power of a single SNP like rs4988236 depends heavily on the genetic background of the individual.
Population Frequency
The frequency of lactase persistence-associated variants varies dramatically across the globe, reflecting different evolutionary pressures related to historical dairy consumption. In Northern European populations, certain variants are found at very high frequencies, while in other regions, such as parts of Africa, the Middle East, and East Asia, different variants are more prevalent. The minor allele frequency for rs4988236 is known to fluctuate, ranging from approximately 0.10 in some non-European ancestries to as high as 0.70 in specific Northern European groups. This wide distribution highlights that lactase persistence is not a single, universal genetic trait but rather a collection of different mutations that have emerged and persisted in various human populations over thousands of years.
Interpreting Your Genetic Information
Understanding your genotype for rs4988236 provides insight into the genetic likelihood of lactase persistence, but it is not a clinical diagnosis for lactose intolerance. Lactose intolerance is a physiological condition characterized by symptoms like bloating, gas, or diarrhea after consuming dairy, which can be influenced by factors beyond genetics, such as gut microbiome composition or secondary health conditions. If you are experiencing digestive symptoms, it is important to consult with a healthcare professional or a registered dietitian. They can help determine if your symptoms are related to lactose malabsorption or other digestive issues. Genetic information should be viewed as a piece of the puzzle rather than a definitive medical answer. Never use genetic test results to make changes to your diet or health management without first discussing them with a qualified clinician.
How common is this variant?
The minor allele frequency for rs4988236 varies significantly, ranging from approximately 0.10 in non-European ancestries to 0.70 in Northern European populations.
Frequently asked questions
Is rs4988236 the same as being lactose intolerant?
No, rs4988236 is a genetic marker associated with the potential for lactase persistence. It does not directly diagnose lactose intolerance, which is a clinical condition defined by symptoms after consuming dairy.
Can I use this SNP to decide if I should eat dairy?
Genetic results should not be used to make dietary decisions. If you suspect you have lactose intolerance, consult a doctor to discuss your symptoms and appropriate testing.
Why do different populations have different lactase persistence genes?
Lactase persistence evolved independently in different human populations as a response to the cultural practice of dairy farming. Consequently, different mutations in the same regulatory region emerged in different parts of the world.
Does this variant affect the MCM6 protein?
No, this variant is located in an intron of the MCM6 gene that acts as a regulatory enhancer for the LCT gene. It does not change the structure or function of the MCM6 protein itself.
Sources & further reading
Educational information only, last refreshed 10/18/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Get my report — $29Related variants in MCM6
While often discussed in the context of lactase persistence, the primary causal variant for lactase persistence is rs4988235 (C/T), which regulates LCT gene expression.
Regulatory enhancer variant upstream of LCT that maintains lactase enzyme activity into adulthood, allowing consumption of dairy without lactose intolerance.
A common variant in the MCM6 gene that determines whether a person can digest lactose (milk sugar) as an adult.
This variant, also known as G/C-14010, is located in the MCM6 gene and acts as a regulatory element for the lactase (LCT) gene, influencing lactase persistence in specific ancestral populations.