CFTR rs121908735: Understanding This Rare Genetic Variant
The rs121908735 variant is a rare genetic change located within the CFTR gene. It is associated with cystic fibrosis, a condition that affects the body's ability to transport chloride ions across cell membranes.
What each genotype means
Typical CFTR function
This genotype represents the most common genetic sequence found in the general population for this specific location in the CFTR gene. It is considered the reference or wild-type sequence, meaning it does not carry the specific variant associated with the studied condition. Individuals with this genotype do not have this specific genetic risk factor for cystic fibrosis.
This is the most common genotype observed across all global populations.
Carrier status
You carry one copy of the variant allele and one copy of the reference allele. In the context of the CFTR gene, carrying one variant is typically associated with being a carrier, which generally does not cause cystic fibrosis symptoms but may be relevant for family planning. Please discuss these results with a genetic counselor or your healthcare provider to understand the implications for your health and family.
This genotype is rare, occurring at a very low frequency in the general population.
Potential clinical significance
You carry two copies of the variant allele. Because the CFTR gene is associated with cystic fibrosis, this genotype may have clinical implications for chloride channel function in epithelial cells. It is essential to discuss these findings with a medical professional or a clinical geneticist to determine if this result correlates with any clinical symptoms or health history.
This genotype is extremely rare in the general population.
What is the rs121908735 Variant?
The rs121908735 variant is a specific single nucleotide polymorphism (SNP) found within the CFTR gene, which is located on chromosome 7. In genetics, a SNP represents a variation at a single position in the DNA sequence. This particular variant is categorized as a trait-associated marker in our catalog, meaning it has been identified in research studies investigating the genetic underpinnings of cystic fibrosis. Because the CFTR gene is quite large and contains many potential sites for variation, researchers track specific rsIDs like rs121908735 to pinpoint exactly where a change occurs. Understanding the location of this variant is the first step in determining how it might influence the production or function of the protein encoded by the CFTR gene.
The Role of the CFTR Gene
The CFTR gene provides the essential instructions for building the cystic fibrosis transmembrane conductance regulator protein. This protein acts as a channel that sits on the surface of epithelial cells, which line various organs including the lungs, pancreas, and liver. Its primary job is to regulate the movement of chloride ions—a component of salt—into and out of these cells. This movement is crucial for maintaining the proper balance of fluids and mucus in the body. When the CFTR gene contains pathogenic variants, the resulting protein may be missing, misfolded, or unable to function correctly. This disruption leads to the production of thick, sticky mucus that can clog airways and obstruct ducts in the pancreas, which is the hallmark of cystic fibrosis.
Research and Evidence Strength
The association between variants in the CFTR gene and cystic fibrosis is well-established in scientific literature. Cystic fibrosis is an autosomal recessive condition, meaning an individual typically needs to inherit two copies of a pathogenic variant—one from each parent—to manifest the classic symptoms of the disease. While many CFTR variants have been extensively studied, the evidence strength for any specific rare variant like rs121908735 can vary based on the number of clinical cases reported and functional studies performed. Current research indicates that this variant is associated with the disruption of chloride channel function. Because cystic fibrosis presents a broad spectrum of clinical severity, researchers continue to study how different variants, including rare ones, contribute to the wide range of symptoms observed in patients.
Population Frequency
The rs121908735 variant is classified as rare across global populations. In genetic research, 'rare' typically means that the variant is found in a very small percentage of the population. Because it is not a common polymorphism, it is not frequently encountered in general population screening programs. The frequency of such variants can also differ significantly based on ancestral background, as certain genetic changes are more prevalent in specific geographic regions or ethnic groups. Because this variant is rare, it is not typically included in standard, first-tier newborn screening panels, which usually focus on the most common pathogenic variants known to cause the majority of cystic fibrosis cases worldwide.
What You Can Do With This Information
Genetic information regarding rare variants should be interpreted with caution and always in the context of a clinical evaluation. If you have received a report mentioning this variant, it is important to understand that a genetic finding is not a medical diagnosis. Cystic fibrosis is a complex condition that requires specialized testing, such as sweat chloride tests or comprehensive genetic sequencing, performed by healthcare professionals. You cannot use this information to self-diagnose or make decisions about your health. If you are concerned about your genetic status or family history, the most appropriate step is to consult with a genetic counselor or a physician who specializes in medical genetics. They can help you understand the clinical significance of your results and discuss whether further diagnostic testing is necessary for you or your family members.
How common is this variant?
The rs121908735 variant is considered rare, appearing at a very low frequency in global population databases.
Frequently asked questions
Is rs121908735 a diagnosis for cystic fibrosis?
No, identifying a genetic variant is not a medical diagnosis. A diagnosis of cystic fibrosis requires clinical evaluation and specialized diagnostic testing by a medical professional.
What should I do if I have this variant?
If you are concerned about this result, you should discuss it with a genetic counselor or your primary care physician. They can provide context based on your personal and family health history.
Why is this variant called rare?
A variant is called rare when it is found in a very small percentage of the general population. Most people do not carry this specific genetic change.
Can I use this information to change my medication?
No. Never change your medication or treatment plan based on genetic information without consulting your clinician or pharmacist first.
Sources & further reading
Educational information only, last refreshed 10/3/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Severe pathogenic mutation (p.Gly542Ter) associated with cystic fibrosis.
Classic cystic fibrosis in-frame 3-bp deletion variant (p.Phe508del / deltaF508) causing misfolding and impaired chloride channel trafficking.
Pathogenic frameshift mutation (c.3659delC) in CFTR linked to cystic fibrosis.
Pathogenic nonsense variant (p.Gly542Ter / G542X) causing autosomal recessive cystic fibrosis when inherited in trans with another CFTR pathogenic allele.
Also known as p.Arg117His (R117H), this CFTR variant is associated with mild or atypical cystic fibrosis and congenital bilateral absence of the vas deferens, with clinical severity influenced by the poly-T tract background.
A CFTR mutation associated with cystic fibrosis and CFTR-related disorders.