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Genetic Archaeology
GENETIC ARCHAEOLOGY // PROFILE

LCT

Lactase

CHR 2
2q21.3

Overview

LCT encodes the enzyme lactase, which breaks down milk sugar (lactose) into glucose and galactose. The C/T-13910 variant determines whether lactase production is maintained into adulthood (lactase persistence) or declines (lactose intolerance).

📍 Chromosomal Position

2q21.3 (Chromosome 2)

🧬 Gene Category

Vitamins

🔬 Inheritance

Autosomal dominant (Persistence)

📊 Prevalence

65% worldwide are lactose intolerant

Function & Significance

Lactase is produced in the small intestine and breaks down lactose into digestible sugars. In most mammals, lactase production decreases after weaning. In humans, a mutation has evolved in some populations that maintains lactase production throughout adulthood.

🌍 Evolutionary Adaptation

Lactase persistence is a relatively recent evolutionary adaptation:

  • Northern Europe: 90-95% lactase persistence
  • Southern Europe: 40-70% lactase persistence
  • East Asia: 5-10% lactase persistence
  • Africa: Varies greatly by region

The mutation emerged about 7,500-10,000 years ago with the domestication of dairy cattle!

🧬 Relevant SNPs

The C/T-13910 variant (rs4988235):

rs4988235
2:135851076
Allele 1

A

/

Allele 2

G

Significance: C/T-13910 Lactase Persistence Variant

• GG (TT): Lactase persistence, can digest milk

• AA (CC): Lactose intolerance, reduced lactase in adulthood

• AG (CT): Partial lactase persistence, individual tolerance levels

🥛 Symptoms of Lactose Intolerance

In cases of lactose intolerance (AA/CC genotype) following milk consumption:

  • Bloating and abdominal pain
  • Diarrhea
  • Nausea
  • Feeling of fullness

Management: Lactose-free products, lactase tablets, and fermented dairy products (yogurt, cheese) are often better tolerated.

📚 Data Sources

The information on this page is based on the following scientific sources:

  • OMIM: #603202 – Online Mendelian Inheritance in Man
  • dbSNP: rs4988235 – SNP Database (NCBI)
  • ClinVar: Clinical Variant Database (NCBI)
  • PubMed: Lactose Intolerance Research
  • WHO: Lactose Intolerance Guidelines

Last Update: February 2026

Biological Function

Lactase breaks down milk sugar (lactose) into glucose and galactose. The C/T-13910 variant regulates lactase persistence in adulthood.

Associated Conditions

Lactose Intolerance
Molecular Analysis

Analyzed Markers

rs4988235 Trait/Pathogenic
Pos: 2:135851076 | Alleles: A/G

C/T-13910 - GG(TT): Lactase persistence, AA(CC): Lactose intolerance