What you carry at this position in your DNA and what research says about it.
Cholesterol and Heart Risk: 10/10 evidence, 10 publications.
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Sample genotype (not yours): C/C
Normal Cholesterol and Heart Risk
Two copies of the typical allele mean your body produces fully functional apolipoprotein B. This allows your liver to efficiently clear LDL cholesterol from your bloodstream, maintaining typical lipid levels.
What this genotype means: Typical LDL cholesterol clearance; No elevated risk for familial hypercholesterolemia.
Sample genotype (not yours): C/T
High Cholesterol and Heart Risk
A single T allele causes familial hypercholesterolemia type B, a condition that significantly raises LDL cholesterol. This occurs because half of your apolipoprotein B proteins cannot properly bind to liver receptors for clearance.
What this genotype means: Significantly elevated LDL cholesterol; Increased risk of premature heart disease; Reduced LDL clearance by the liver.
Sample genotype (not yours): T/T
Severely High Cholesterol and Heart Risk
Two copies of the T allele cause a severe form of familial hypercholesterolemia. With none of your apolipoprotein B proteins functioning normally, LDL cholesterol levels can reach dangerously high levels.
What this genotype means: Severely elevated LDL cholesterol; Very high risk of early-onset cardiovascular disease; Extremely impaired LDL clearance.
Gene function and biological role
Gene Function: The APOB gene provides instructions for making apolipoprotein B, a critical component of lipid-transporting particles in the bloodstream [1]. It produces two main versions: apolipoprotein B-48 in the intestine and apolipoprotein B-100 in the liver [1]. Apolipoprotein B-100 acts as a structural backbone for low-density lipoprotein (LDL) particles, which carry cholesterol to cells [1]. This protein contains a crucial receptor-binding region that allows LDL to attach to receptors on liver cells, facilitating its clearance from the blood [2]. Without functional apolipoprotein B, cholesterol accumulates in the bloodstream, leading to severe cardiovascular risks [3].
Variant Impact: Replacing the amino acid arginine with glutamine at position 3527 of the apolipoprotein B-100 protein (p.Arg3527Gln) alters a critical functional region [4]. This specific change occurs directly within the receptor-binding domain of the protein [2]. Because of this alteration, the mutated apolipoprotein B-100 cannot bind properly to LDL receptors on liver cells [1]. This failure in binding severely impairs the clearance of LDL particles from the bloodstream, causing them to accumulate [5]. Consequently, this single-letter change is a well-established genetic cause of familial hypercholesterolemia type B [3].
Location: APOB. Chromosome 2 · 2p24.1 · 21.0 Mb
Origin Story: The T allele is highly enriched in the Old Order Amish of Lancaster County, Pennsylvania, due to a founder effect, where a small group of ancestors passed it down, resulting in a carrier frequency of up to 12% compared to less than 0.1% globally.
Estimated prevalence by population
Global 99.9%; European 99.9%; African > 99.9%; East Asian 100.0%; South Asian 100.0%; Americas 99.9%; Ashkenazi 100.0%; Finnish 100.0%; Middle Eastern 100.0%; Amish 86.9%.
Estimated CC genotype frequency.
Global 0.1%; European 0.1%; African < 0.1%; East Asian 0.0%; South Asian 0.0%; Americas 0.1%; Ashkenazi 0.0%; Finnish 0.0%; Middle Eastern 0.0%; Amish 12.7%.
Estimated CT genotype frequency.
Global < 0.1%; European < 0.1%; African < 0.1%; East Asian 0.0%; South Asian 0.0%; Americas < 0.1%; Ashkenazi 0.0%; Finnish 0.0%; Middle Eastern 0.0%; Amish 0.5%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Cardiovascular & Metabolic
Lipids & Cholesterol
LDL Cholesterol. Evidence: 10/10. Source: PMID 24507774. Typical.
Apolipoprotein B. Evidence: 10/10. Source: PMID 34226706. Typical.
Total Cholesterol. Evidence: 10/10. Source: PMID 34226706. Typical.
Heart Disease
Heart Disease. Evidence: 7/10. Source: PMID 9603795. Typical Risk.
Nutrition & Metabolism
Blood Chemistry & Metabolites
Sphingomyelin Levels. Evidence: 6/10. Source: PMID 35393526. Typical.
Showing effects for C/T genotype
LDL Cholesterol. Evidence: 10/10. Source: PMID 24507774. Elevated.
Apolipoprotein B. Evidence: 10/10. Source: PMID 34226706. Elevated.
Total Cholesterol. Evidence: 10/10. Source: PMID 34226706. Elevated.
Heart Disease. Evidence: 7/10. Source: PMID 9603795. Increased Risk.
Sphingomyelin Levels. Evidence: 6/10. Source: PMID 35393526. Increased.
Showing effects for T/T genotype
LDL Cholesterol. Evidence: 10/10. Source: PMID 24507774. Severely Elevated.
Apolipoprotein B. Evidence: 10/10. Source: PMID 34226706. Severely Elevated.
Total Cholesterol. Evidence: 10/10. Source: PMID 34226706. Severely Elevated.
Heart Disease. Evidence: 7/10. Source: PMID 9603795. Highly Increased Risk.
Sphingomyelin Levels. Evidence: 6/10. Source: PMID 35393526. Highly Increased.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
The reference C allele is the most common genetic profile globally, occurring in over 99.9% of the population. This genotype ensures that your apolipoprotein B-100 proteins have a normal arginine residue at position 3527, allowing proper binding to LDL receptors [1]. As a result, your liver can effectively remove low-density lipoprotein (LDL) particles from circulation, preventing abnormal cholesterol buildup [2]. Your genetic risk for familial hypercholesterolemia type B at this specific locus is not elevated [3]. Maintaining a balanced diet and regular exercise will help support your baseline cardiovascular health.
Typical LDL cholesterol clearance; No elevated risk for familial hypercholesterolemia.
Sample genotype: CT (Heterozygous)
A single copy of the T allele leads to a condition known as familial defective apolipoprotein B-100, or familial hypercholesterolemia type B [1]. Because the mutated protein cannot bind effectively to LDL receptors, LDL cholesterol particles accumulate in the bloodstream [2]. This chronic elevation of cholesterol starting from a young age significantly increases the risk of premature coronary artery disease and calcification [3]. While rare globally, this variant is highly prevalent in the Old Order Amish population due to a founder effect [3]. Early clinical monitoring and lipid-lowering strategies are typically recommended to manage cardiovascular risk.
Significantly elevated LDL cholesterol; Increased risk of premature heart disease; Reduced LDL clearance by the liver.
Sample genotype: TT (Homozygous)
Two copies of the T allele represent an extremely rare genetic profile that results in homozygous familial defective apolipoprotein B-100 [1]. In this state, virtually all of your apolipoprotein B-100 proteins lack the ability to bind to LDL receptors [2]. This leads to a profound accumulation of small dense LDL particles in the blood, which are highly prone to causing arterial plaques [3]. Without intervention, cholesterol levels can reach extremely high thresholds, dramatically accelerating the development of cardiovascular disease from early childhood [3]. This condition requires close medical supervision and aggressive lipid-lowering therapies to protect heart health.
Severely elevated LDL cholesterol; Very high risk of early-onset cardiovascular disease; Extremely impaired LDL clearance.
Variants with shared genetic architecture
rs1042034 · APOB Gene · Chr 2 · Cholesterol and Lipids
rs1367117 · APOB Gene · Chr 2 · Cholesterol Levels
rs4665710 · APOB Gene · Chr 2 · Blood Lipid Levels
The molecular mechanism for the genetic disorder familial defective apolipoprotein B100.
Content updated August 2026.
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