HEXA rs121908009: What Your Genotype Means
The rs121908009 variant in the HEXA gene is a specific genetic change known as a splice junction mutation. It is associated with the development of Tay-Sachs disease, a rare, autosomal recessive condition that affects the nervous system.
What each genotype means
Typical HEXA gene profile
This genotype represents the common, non-mutated sequence for this specific location in the HEXA gene. Individuals with this profile do not carry this specific splice junction mutation associated with Tay-Sachs disease.
This is the most common genotype found in the vast majority of the global population.
Tay-Sachs carrier status
This genotype indicates you are a carrier of the c.1073+1G>A mutation in the HEXA gene. Carriers typically do not show symptoms of Tay-Sachs disease, but they have a 25% chance of passing this mutation to their children, which could lead to the condition if the other biological parent is also a carrier.
This genotype is found in approximately 0.002 of the Ashkenazi Jewish population and is significantly less common, occurring in less than 0.0001 of non-Jewish populations.
Potential Tay-Sachs disease risk
This genotype indicates the presence of two copies of the c.1073+1G>A mutation, which is a known cause of infantile Tay-Sachs disease. This condition is a serious, autosomal recessive neurodegenerative disorder that results from the absence of functional hexosaminidase A enzyme activity. Please consult with a medical geneticist or healthcare provider to discuss these results and their clinical implications.
This genotype is extremely rare in the general population.
Understanding the Variant
The variant rs121908009, technically identified as c.1073+1G>A, is a single nucleotide change located within the HEXA gene on chromosome 15. This specific location is a splice donor site, which is a critical sequence that tells the cell's machinery how to correctly process the gene's instructions into a functional protein. When this site is altered, the cell may fail to properly assemble the messenger RNA, often leading to a non-functional or absent protein product. Because this variant disrupts the normal splicing process, it is classified as a pathogenic variant in the context of clinical genetics. It is one of many known mutations in the HEXA gene that can interfere with the production of the hexosaminidase A enzyme, which is essential for cellular health.
The Role of the HEXA Gene
The HEXA gene provides the instructions for creating the alpha-subunit of an enzyme called beta-hexosaminidase A. This enzyme is primarily located within lysosomes, which are the recycling centers of the cell. Its main job is to break down a fatty substance known as GM2 ganglioside. In a healthy individual, this enzyme ensures that GM2 ganglioside is recycled efficiently. However, when mutations like rs121908009 occur, the body produces little to no functional hexosaminidase A. Without this enzyme, GM2 ganglioside accumulates to toxic levels, particularly within the nerve cells of the brain and spinal cord. This accumulation leads to the progressive neurodegeneration characteristic of Tay-Sachs disease, which can manifest in infantile, juvenile, or adult forms depending on the residual enzyme activity.
Research and Clinical Evidence
Research has established a strong link between this variant and Tay-Sachs disease. Because the condition is inherited in an autosomal recessive pattern, an individual must typically inherit two copies of a pathogenic HEXA mutation—one from each parent—to manifest the disease. If an individual carries only one copy, they are considered a carrier and generally do not show symptoms of the disorder. The evidence for rs121908009 as a disease-causing variant is well-documented in clinical databases, where it is recognized for its role in preventing the production of functional hexosaminidase A. While the association with the disease is clear, the clinical severity can vary based on the specific combination of mutations present in an individual. Genetic counseling is recommended for those who identify this variant in their results to understand the implications for family planning.
Population Frequency
The frequency of the rs121908009 variant varies significantly across different ancestral groups. It is most frequently observed in individuals of Ashkenazi Jewish descent, with a reported carrier frequency of approximately 0.002. In contrast, the variant is much rarer in the general non-Jewish population, where its frequency is estimated to be less than 0.0001. These differences highlight the importance of ancestry in genetic screening and the historical prevalence of certain founder mutations within specific communities. Because the variant is rare, most people will not carry it, but those with a family history of Tay-Sachs or those from high-risk populations may choose to undergo targeted carrier screening to assess their reproductive risks.
What You Can Do With This Information
Information about your carrier status for rs121908009 is primarily useful for reproductive planning and understanding your family's genetic health. If you discover that you are a carrier, it does not mean you have or will develop Tay-Sachs disease, as the condition requires two pathogenic copies. However, if both partners are carriers of a HEXA mutation, there is a 25% chance with each pregnancy that the child will inherit the condition. This information should not be used for self-diagnosis or to make medical decisions without professional guidance. If you have concerns about your results or your family history, the most appropriate step is to consult with a board-certified genetic counselor or a medical geneticist. They can provide context, explain the risks, and discuss available testing options for you and your partner.
How common is this variant?
The variant has a frequency of 0.002 in Ashkenazi Jewish populations and is found at a frequency of less than 0.0001 in non-Jewish populations.
Frequently asked questions
What is the rs121908009 variant?
The rs121908009 variant is a specific genetic mutation in the HEXA gene that disrupts the normal splicing of the gene's instructions. This disruption prevents the body from producing a functional hexosaminidase A enzyme.
Does having this variant mean I have Tay-Sachs disease?
Not necessarily. Tay-Sachs is an autosomal recessive condition, meaning you generally need two copies of a pathogenic mutation to have the disease. If you have only one copy, you are a carrier and typically do not have the disease.
Should I be tested for Tay-Sachs?
Carrier screening is often recommended for individuals of Ashkenazi Jewish descent or those with a family history of Tay-Sachs disease. You should discuss the appropriateness of this testing with your healthcare provider or a genetic counselor.
Can this variant be treated?
There is currently no cure for Tay-Sachs disease, and management focuses on supportive care to address symptoms. If you have concerns about your genetic status, please consult a medical professional for personalized advice.
Sources & further reading
Educational information only, last refreshed 9/23/2026. Not medical advice — these associations describe population statistics, not individual predictions.
Curious what your genotype is for rs121908009?
Upload a raw DNA file from 23andMe, AncestryDNA, MyHeritage, or FamilyTreeDNA and see this variant — plus thousands more — interpreted in your full report.
Get my report — $29Related variants in HEXA
Canonical splice junction variant (c.1073+1G>A) causing Tay-Sachs disease.
Pathogenic splice-junction variant (c.1073+1G>A / IVS9+1G>A) causing Tay-Sachs disease when in compound heterozygosity or homozygosity.
Pathogenic splice donor variant (c.1421+1G>C) in HEXA underlying carrier status for autosomal recessive infantile Tay-Sachs disease.
This HEXA variant is associated with Tay-Sachs disease, particularly late-onset forms.
Pathogenic splice junction mutation (c.1421+1G>C) in HEXA leading to Tay-Sachs disease.
Pathogenic HEXA splice donor site mutation (c.1073+1G>A) causing Tay-Sachs disease, common in carrier screening panels for Ashkenazi Jewish and French Canadian ancestry.