What you carry at this position in your DNA and what research says about it.
Lynch Syndrome Risk: 7/10 evidence, 1 publications.
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Sample genotype (not yours): G/G
Typical Cancer Risk
Normal mismatch repair function is expected, resulting in a typical risk of Lynch syndrome-associated cancers.
What this genotype means: Typical DNA repair function; No inherited Lynch syndrome risk.
Sample genotype (not yours): G/GA
Highly Increased Lynch Syndrome Risk
Disruption of the MLH1 gene by the GA insertion allele significantly increases the risk of colorectal and other Lynch syndrome-associated cancers.
What this genotype means: Deficient DNA mismatch repair; Highly elevated risk of colorectal cancer; Increased risk of endometrial and ovarian cancers.
Sample genotype (not yours): GA/GA
Severe mismatch repair deficiency occurs when two copies of the GA insertion allele are present. This rare genotype is associated with a highly elevated risk of early-onset cancers requiring intensive medical management.
What this genotype means: Severe DNA mismatch repair deficiency; Extremely high risk of early-onset cancers; Requires intensive pediatric/adult oncology surveillance.
Gene function and biological role
Gene Function: The MLH1 gene encodes a critical protein involved in mismatch repair, a cellular system that corrects errors made during DNA replication. When functioning normally, MLH1 helps maintain genomic stability and prevents mutations from accumulating in the genome [1]. Mutations in MLH1 can lead to a deficiency in DNA mismatch repair, causing microsatellite instability. This deficiency is a hallmark of Lynch syndrome, an inherited condition that dramatically increases the risk of colorectal and other cancers.
Variant Impact: The rs63750057 variant represents an insertion of an adenine nucleotide in the MLH1 gene. This insertion causes a frameshift mutation, altering the reading frame of the genetic code from codon 14 onward [1]. The resulting protein is truncated and non-functional, rendering it unable to participate in mismatch repair. Consequently, individuals carrying this insertion have a significantly elevated risk of developing Lynch syndrome-associated cancers.
Key Insight: A single copy of the GA insertion allele is sufficient to cause Lynch syndrome, a hereditary cancer predisposition.
Location: MLH1. Chromosome 3 · 3p22.2 · 37.0 Mb
Estimated prevalence by population
No frequency data available
This variant is not present in the gnomAD database.
Showing effects for G/G genotype
Cancer & Oncology
Colorectal Cancer
Lynch Syndrome. Evidence: 7/10. Source: PMID 15713769. Typical Risk.
Colorectal Cancer. Evidence: 7/10. Source: PMID 15713769. Typical Risk.
Gynecological Cancers
Endometrial Cancer. Evidence: 7/10. Source: PMID 15713769. Typical Risk.
Ovarian Cancer. Evidence: 7/10. Source: PMID 15713769. Typical Risk.
Showing effects for G/GA genotype
Lynch Syndrome. Evidence: 7/10. Source: PMID 15713769. Highly Increased Risk.
Colorectal Cancer. Evidence: 7/10. Source: PMID 15713769. Highly Increased Risk.
Endometrial Cancer. Evidence: 7/10. Source: PMID 15713769. Increased Risk.
Ovarian Cancer. Evidence: 7/10. Source: PMID 15713769. Increased Risk.
Showing effects for GA/GA genotype
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Normal mismatch repair function is expected because the MLH1 gene produces a fully functional protein [1]. This protein plays a vital role in correcting DNA replication errors, thereby maintaining genomic integrity and preventing tumor development. Because mismatch repair remains intact, there is no inherited predisposition to Lynch syndrome or its associated cancers.
Typical DNA repair function; No inherited Lynch syndrome risk.
Sample genotype: GGA (Heterozygous)
Disruption of the normal reading frame occurs due to the GA insertion allele, leading to a non-functional MLH1 protein [1]. Because Lynch syndrome is inherited in an autosomal dominant manner, a single mutated copy is sufficient to cause the syndrome. This condition is characterized by a high lifetime risk of colorectal cancer, often developing at an earlier age than in the general population. It also elevates the risk for endometrial, ovarian, gastric, and other cancers.
Deficient DNA mismatch repair; Highly elevated risk of colorectal cancer; Increased risk of endometrial and ovarian cancers.
Sample genotype: GAGA (Homozygous)
Presence of two copies of the GA insertion allele is extremely rare and typically associated with constitutional mismatch repair deficiency. This severe condition results in a complete lack of functional MLH1 protein, leading to early-onset cancers in childhood or young adulthood [1]. Affected individuals face a very high risk of colorectal, brain, and hematological malignancies.
Severe DNA mismatch repair deficiency; Extremely high risk of early-onset cancers; Requires intensive pediatric/adult oncology surveillance.
Variants with shared genetic architecture
rs111052004 · MLH1 Gene · Chr 3 · Lynch Syndrome Risk
rs11541859 · MLH1 Gene · Chr 3 · Lynch Syndrome Risk
rs1799977 · MLH1 Gene · Chr 3 · Lynch Syndrome Risk
Conversion analysis for mutation detection in MLH1 and MSH2 in patients with colorectal cancer.
Content updated August 2026.
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