GALT rs75947754: Understanding the Q188R Variant
The rs75947754 variant in the GALT gene, commonly known as p.Gln188Arg (Q188R), is a genetic change associated with classic galactosemia. This condition affects how the body processes galactose, a sugar found in milk and dairy products.
What each genotype means
Typical GALT enzyme activity
This genotype represents the most common, functional version of the GALT gene. Individuals with this profile typically produce normal levels of the galactose-1-phosphate uridylyltransferase enzyme, which is necessary for processing galactose from the diet.
This is the most common genotype found in the general population across all ancestries.
GALT variant carrier status
You carry one copy of the Q188R variant (also known as c.563A>G) and one typical copy of the GALT gene. Carriers are generally asymptomatic and produce sufficient enzyme activity to process galactose normally, though you should discuss this result with a genetic counselor or clinician if you are planning a family, as there is a chance of passing the variant to offspring.
Carried by roughly 1 in 107 people of non-Traveller European ancestry, and approximately 1 in 11 among the Traveller population.
Classic galactosemia risk
This genotype indicates the presence of two copies of the Q188R variant, which is associated with classic galactosemia. This condition results in absent or barely detectable GALT enzyme activity, requiring strict dietary management of lactose and galactose intake under medical supervision.
This genotype is rare in the general population, occurring primarily in individuals who have inherited the variant from both parents.
What is the rs75947754 Variant?
The rs75947754 variant is a specific change in the DNA sequence of the GALT gene. Scientifically, it is classified as a missense mutation, meaning it results in a single amino acid substitution in the protein product. Specifically, an A to G transition in exon 6 of the gene causes the amino acid glutamine at position 188 to be replaced by arginine. This change is often referred to as Q188R. Because this variant can significantly impact the function of the resulting enzyme, it is frequently included in expanded carrier screening panels to help identify individuals who may carry a copy of this genetic change.
The Role of the GALT Gene
The GALT gene provides instructions for making an enzyme called galactose-1-phosphate uridylyltransferase. This enzyme is essential for the body to break down galactose, a simple sugar found in many foods, particularly dairy products like breast milk and cow's milk. The enzyme converts galactose-1-phosphate into glucose-1-phosphate, which the body can then use for energy. When the GALT gene contains certain pathogenic variants, the enzyme may be missing or non-functional. This leads to an accumulation of galactose and its toxic byproducts in the body, which can cause damage to various organs, including the liver, brain, and eyes, if not managed appropriately.
Research and Clinical Associations
Research has established a strong link between the Q188R variant and classic galactosemia, a rare metabolic disorder. Classic galactosemia is inherited in an autosomal recessive pattern, meaning an individual typically needs to inherit two copies of a pathogenic variant—one from each parent—to manifest the condition. The Q188R variant is considered one of the most common pathogenic variants associated with this disorder. While the evidence for its pathogenicity is well-documented in clinical literature, the severity of the condition can vary. Early diagnosis, often through newborn screening programs that measure GALT enzyme activity or galactose levels, is critical for initiating dietary management, which can prevent or mitigate many of the severe symptoms associated with the condition.
Population Frequency
The frequency of the rs75947754 variant varies across different ancestral populations. In European populations, the carrier frequency is estimated to be approximately 1 in 100 to 1 in 150. Because this is a recessive condition, most carriers do not exhibit symptoms of galactosemia. However, understanding the prevalence of this variant is important for genetic counseling and population health screening. It is important to note that allele frequencies can differ significantly between ethnic groups, and ongoing research continues to refine these estimates as more diverse genomic data becomes available.
What This Information Means for You
If you have received information about your status regarding the rs75947754 variant, it is important to understand that this is a carrier status marker. Being a carrier generally does not mean you have the disease, but it does mean you carry one copy of the variant. If you are concerned about your genetic status or family history, the most appropriate step is to consult with a certified genetic counselor or a medical professional. They can provide context based on your specific results and family history. Never use genetic information to make medical decisions or dietary changes without professional guidance, as these should always be managed by a clinician who understands your full health profile.
How common is this variant?
The carrier frequency for the rs75947754 variant is approximately 1 in 100 to 1 in 150 in European populations.
Frequently asked questions
What is classic galactosemia?
Classic galactosemia is a rare genetic disorder where the body cannot properly break down the sugar galactose. It is caused by a deficiency in the GALT enzyme and requires careful dietary management.
Does having the Q188R variant mean I have galactosemia?
Not necessarily. Because galactosemia is a recessive condition, you typically need two copies of a pathogenic variant to have the disease. If you have only one copy, you are a carrier.
How is galactosemia diagnosed?
Galactosemia is often detected through newborn screening programs that test for GALT enzyme activity or elevated galactose levels in the blood. Confirmatory testing usually involves genetic analysis of the GALT gene.
Can I change my diet based on this genetic result?
You should not make any dietary changes based on a genetic test result without consulting a doctor or a registered dietitian. They can determine if any medical intervention or dietary adjustment is necessary for your specific health needs.
Sources & further reading
Educational information only, last refreshed 10/13/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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