rs4939827

A SNP in the SMAD7 gene on chromosome 18. Its most notable genotype is T;T: 1x risk for colorectal cancer

Gene
SMAD7
Location
Chr 1848,927,093 (GRCh38)
Highest magnitude
1.5Minor
Tested on
23andMe, AncestryDNA
Minor allele frequency
38%

Genotypes

As shown in 23andMe and AncestryDNA files.

  1. C;CGood0.73x decreased risk for colorectal cancerMinor · 1.045% of people
  2. C;TGood0.86x decreased risk for colorectal cancerMinor · 1.042% of people
  3. T;TMost notableBad1x risk for colorectal cancerMinor · 1.514% of people

On SNPedia: (C;C), (C;T), (T;T). Magnitude rates how notable a genotype is from 0 to 10, not how risky it is.

Frequency

Share of each genotype in 11 HapMap populations.

  • AverageC;C 45% C;T 42% T;T 14%
  • European ancestry (Utah)C;C 29% C;T 47% T;T 24%
  • Han Chinese (Beijing)C;C 58% C;T 35% T;T 7%
  • Japanese (Tokyo)C;C 69% C;T 27% T;T 4%
  • Yoruba (Nigeria)C;C 58% C;T 33% T;T 9%
  • African ancestry (Southwest US)C;C 37% C;T 54% T;T 9%
  • Chinese (Denver)C;C 51% C;T 38% T;T 11%
  • Gujarati IndianC;C 42% C;T 45% T;T 14%
  • Luhya (Kenya)C;C 54% C;T 34% T;T 13%
  • Mexican ancestry (Los Angeles)C;C 36% C;T 50% T;T 14%
  • Maasai (Kenya)C;C 47% C;T 38% T;T 15%
  • TuscanC;C 13% C;T 56% T;T 31%

Conditions, medicines and genes

Other SMAD7 SNPs

All SMAD7 SNPs

Notes

From SNPedia

Notes

rs4939827 is one of 3 SNPs in the SMAD7 gene associated with risk for colorectal cancer, based on a large study (7,400+ cases) conducted in the UK. The odds ratios show a decreased risk for the minor rs4939827(C) allele; the OR for (C;C) homozygotes is 0.73 (CI: 0.66-0.8), and for (C;T) heterozygotes 0.86 (CI: 0.79-0.92), overall p=1x10 -12 .

Source and license

Adapted from rs4939827 on SNPedia, using a snapshot taken October 16, 2026. SNPedia content is shared under CC BY-NC-SA 3.0 US, and this page is shared under the same license.

SNPedia is a community-edited wiki. Its entries can be incomplete, out of date or wrong, and nothing here is a diagnosis or medical advice. Magnitude is a community rating of how interesting a genotype is, not a risk score.