What you carry at this position in your DNA and what research says about it.
Lung Cancer Risk: 10/10 evidence, 27 publications.
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Sample genotype (not yours): C/C
Typical Lung Cancer Risk
This genotype is associated with typical baseline risks for lung cancer and clonal hematopoiesis. It represents the most common genetic profile globally.
What this genotype means: Typical baseline risk of lung and ovarian cancers; Lower risk of clonal hematopoiesis; Slightly larger red blood cell volume.
Sample genotype (not yours): A/A
Increased Lung Cancer Risk
Carrying two copies of the A allele is linked to a higher risk of lung cancer, ovarian cancer, and clonal hematopoiesis, alongside longer telomeres.
What this genotype means: Increased risk of lung adenocarcinoma; Higher risk of clonal hematopoiesis; Higher platelet and white blood cell counts.
Sample genotype (not yours): C/A
Slightly Elevated Lung Cancer Risk
Carrying one copy of the A allele is linked to a slightly higher risk of lung cancer and clonal hematopoiesis. It also correlates with longer telomeres.
What this genotype means: Slightly higher risk of lung adenocarcinoma; Modestly increased risk of clonal hematopoiesis; Slightly higher platelet and white blood cell counts.
Gene function and biological role
Gene Function: The TERT gene encodes telomerase reverse transcriptase, the essential catalytic subunit of the telomerase enzyme. Telomerase maintains the length of telomeres, which are the protective caps at the ends of chromosomes that naturally shorten as cells age and divide [1]. By replenishing these caps, the enzyme plays a central role in determining cellular lifespan and genomic stability [1]. However, while active telomerase prevents cellular senescence, its overactivity can enable abnormal cells to replicate indefinitely [2]. Consequently, TERT regulation represents a critical biological balance between healthy cellular longevity and the development of various cancers [2].
Variant Impact: The rs7705526 variant is an intron variant located within the TERT gene that influences how the gene is expressed. The minor A allele is associated with increased promoter activity, leading to higher telomerase expression and longer relative telomere length [1]. While longer telomeres are linked to cellular longevity, this increased replication potential also makes it easier for mutated cells to persist [1]. As a result, the variant alters susceptibility to several hematological conditions and solid tumors [2]. Conversely, the common C allele is associated with lower promoter activity and shorter telomeres, which acts as a natural barrier against uncontrolled cell division [1].
Key Insight: This variant highlights a fundamental evolutionary trade-off where genetic factors that promote longer telomeres and cellular longevity also increase the risk of developing several types of cancer.
Location: TERT. Chromosome 5 · 5p15.33 · 1.3 Mb
Estimated prevalence by population
Global 50.7%; European 44.7%; African 66.1%; East Asian 37.0%; South Asian 33.4%; Americas 52.0%; Ashkenazi 38.5%; Finnish 47.2%; Middle Eastern 29.6%; Amish 47.2%.
Estimated CC genotype frequency.
Global 40.3%; European 44.3%; African 30.4%; East Asian 47.7%; South Asian 48.8%; Americas 40.2%; Ashkenazi 47.1%; Finnish 43.0%; Middle Eastern 49.6%; Amish 43.0%.
Estimated CA genotype frequency.
Global 9.0%; European 11.0%; African 3.5%; East Asian 15.4%; South Asian 17.8%; Americas 7.8%; Ashkenazi 14.4%; Finnish 9.8%; Middle Eastern 20.7%; Amish 9.8%.
Estimated AA genotype frequency.
Showing effects for C/C genotype
Cancer & Oncology
Lung Cancer
Lung Cancer. Evidence: 10/10. Source: PMID 28604730. Typical Risk.
Blood Cancers
Clonal Hematopoiesis. Evidence: 9/10. Source: PMID 35835912. Typical Risk.
Gynecological Cancers
Ovarian Cancer. Evidence: 6/10. Source: PMID 28346442. Typical Risk.
Cardiovascular & Metabolic
Blood Cell & Iron Traits
Platelet Count. Evidence: 10/10. Source: PMID 32888493. Typical.
Red Blood Cell Size. Evidence: 10/10. Source: PMID 32888493. Slightly Larger.
Showing effects for A/A genotype
Lung Cancer. Evidence: 10/10. Source: PMID 28604730. ~1.3x Higher Risk.
Clonal Hematopoiesis. Evidence: 9/10. Source: PMID 35835912. Increased Risk.
Ovarian Cancer. Evidence: 6/10. Source: PMID 28346442. Increased Risk.
Platelet Count. Evidence: 10/10. Source: PMID 32888493. Higher.
Red Blood Cell Size. Evidence: 10/10. Source: PMID 32888493. Slightly Smaller.
Showing effects for C/A genotype
Lung Cancer. Evidence: 10/10. Source: PMID 28604730. ~1.2x Higher Risk.
Clonal Hematopoiesis. Evidence: 9/10. Source: PMID 35835912. Slightly Increased.
Ovarian Cancer. Evidence: 6/10. Source: PMID 28346442. Slightly Increased.
Platelet Count. Evidence: 10/10. Source: PMID 32888493. Slightly Higher.
Red Blood Cell Size. Evidence: 10/10. Source: PMID 32888493. Typical.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Carrying two copies of the C allele is associated with typical baseline risks for several malignancies, including lung cancer and ovarian cancer [1] [2]. Because the C allele is linked to lower TERT promoter activity, telomerase expression remains at a standard level, which naturally limits the replication potential of abnormal cells [1]. This lower activity helps protect against clonal hematopoiesis, a condition where mutated blood stem cells expand abnormally [3]. However, this lower telomerase activity is also associated with shorter relative telomere length over time [1]. On the blood front, this genotype is linked to slightly larger red blood cells but lower overall platelet and white blood cell counts [4]. Overall, this profile avoids the elevated oncological risks associated with the minor variant allele.
Typical baseline risk of lung and ovarian cancers; Lower risk of clonal hematopoiesis; Slightly larger red blood cell volume.
Sample genotype: AA (Homozygous)
Having two copies of the A allele significantly increases TERT promoter activity, resulting in longer telomeres and enhanced cellular proliferative capacity [1]. Although longer telomeres are linked to cellular longevity, they also facilitate the survival and expansion of abnormal cell lineages [1]. Consequently, this genotype is associated with an approximate 1.28-fold increased risk of lung adenocarcinoma [2]. It also elevates the risk of clonal hematopoiesis, a state characterized by the clonal expansion of mutated blood stem cells [3]. Furthermore, research links this homozygous profile to higher risks of ovarian cancer and myeloproliferative disorders [4] [5]. On standard blood tests, this genotype is associated with higher platelet, neutrophil, and white blood cell counts, as well as smaller red blood cells [6].
Increased risk of lung adenocarcinoma; Higher risk of clonal hematopoiesis; Higher platelet and white blood cell counts.
Sample genotype: CA (Heterozygous)
This heterozygous genotype is associated with a modest increase in the risk of developing lung cancer, particularly lung adenocarcinoma [1]. The presence of the A allele increases TERT gene expression, which leads to longer telomeres and greater cellular replication capacity [2]. While longer telomeres are generally associated with slower cellular aging, they also provide a survival advantage to pre-cancerous cells [2]. This genotype also slightly elevates the risk of clonal hematopoiesis, where specific mutated blood cell clones multiply [3]. Additionally, studies show a minor increase in susceptibility to ovarian cancer and certain blood-related disorders [4] [5]. In routine blood panels, this genetic profile may correlate with slightly higher platelet and white blood cell counts alongside slightly smaller red blood cells [6].
Slightly higher risk of lung adenocarcinoma; Modestly increased risk of clonal hematopoiesis; Slightly higher platelet and white blood cell counts.
Variants with shared genetic architecture
rs2242652 · TERT Gene · Chr 5 · Cancer Risk Trade-offs
rs2735940 · TERT Gene · Chr 5 · Colorectal Cancer Risk
rs2853677 · TERT Gene · Chr 5 · Cancer Susceptibility
Identification of 12 new susceptibility loci for different histotypes of epithelial ovarian cancer.
Inherited myeloproliferative neoplasm risk affects haematopoietic stem cells.
Content updated August 2026.
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