gnomAD Carrier Frequency Calculator
A free, browser-based research tool to calculate carrier frequency and recurrence risk for autosomal recessive conditions. Powered by real population allele frequency data from the Genome Aggregation Database (gnomAD), the calculator provides population-specific estimates across multiple ancestries and generates documentation text in German and English. For research and educational use only.
Key Features
- Real Population Data from gnomAD Retrieves current allele frequencies directly from the gnomAD GraphQL API, covering more than 800,000 sequenced individuals across gnomAD v4.1, v3.1.2, and v2.1.1.
- Multiple Ancestries and Founder Effect Detection Compare carrier frequencies across African/African American, Admixed American, Ashkenazi Jewish, East Asian, Finnish, Non-Finnish European, Middle Eastern, and South Asian populations. The tool automatically flags ancestries where carrier frequency is significantly elevated, helping to identify potential founder effects.
- Automated Variant Filtering Automatically includes high-confidence loss-of-function variants (LoF HC) and ClinVar pathogenic or likely pathogenic variants, applying the same evidence standards used in clinical genetics practice. No manual literature curation required.
- Clinical Text Generation Generates structured documentation text ready to paste directly into patient letters or genetic counseling reports. Supports German and English, with configurable gender-inclusive language styles (using *, :, or / forms) to meet documentation requirements in German-speaking countries.
- Recurrence Risk Calculation Calculates the probability that both parents are carriers and the resulting recurrence risk for each pregnancy, following Hardy-Weinberg principles. Covers affected patient, confirmed carrier, and family member scenarios.
- Offline-Capable Progressive Web App Installable on desktop and mobile as a PWA. Once installed, the interface works without an internet connection; only the gnomAD API calls require connectivity.
How It Works
- Search for a gene. Enter the HGNC gene symbol (for example, CFTR or PKD1). The tool queries gnomAD and confirms the gene exists in the selected dataset.
- Select the patient status. Choose whether the patient is an affected individual, a confirmed carrier, or a family member. This determines which recurrence risk scenario the output text will describe.
- Review variants. The tool fetches all qualifying variants for the gene and displays them with their allele frequencies by ancestry. You can inspect the variant list and adjust filters if needed.
- Get results. Carrier frequency and recurrence risk are calculated per population. Choose the relevant ancestry, then copy the generated clinical documentation text directly into your report.
Frequently Asked Questions
How do I calculate carrier frequency from gnomAD data?
The calculator sums the allele frequencies of all pathogenic and high-confidence loss-of-function variants for a gene to estimate the total disease allele frequency (q). It then applies the Hardy-Weinberg equation: carrier frequency = 2pq, where p = 1 - q. Because gnomAD covers hundreds of thousands of individuals, this approach yields more reliable population-level estimates than using disease prevalence figures from the literature alone.
What populations are available?
gnomAD reports allele frequencies for eight ancestry groups: African/African American, Admixed American, Ashkenazi Jewish, East Asian, Finnish, Non-Finnish European, Middle Eastern, and South Asian. A global (combined) frequency is also available. The calculator displays all populations simultaneously so you can select the one that best matches your patient's genetic background. For patients with mixed or unknown ancestry, the global frequency provides a conservative estimate.
Is this tool free to use?
Yes, this tool is completely free. It is an open-source project hosted on GitHub Pages and queries the publicly available gnomAD API directly from your browser. No registration, subscription, or institutional login is required. The source code is available on GitHub for review, adaptation, and contribution.
Can I use these results in clinical practice?
The calculator is designed to support clinical documentation workflows and is used routinely in genetic counseling. However, it is intended as a decision-support tool for research and educational purposes. Population-based allele frequencies are estimates and may not capture all pathogenic variants or reflect every patient's individual risk. Results should be interpreted by a qualified genetics professional and, where required, confirmed by an accredited clinical laboratory before use in formal clinical reports.
What is carrier frequency?
Carrier frequency is the proportion of individuals in a population who carry one pathogenic copy of a recessive disease gene. Carriers have one normal allele and one disease-causing allele. Because one functional copy is sufficient, carriers are typically unaffected but can pass the pathogenic allele to their children. When two carriers have children together, each pregnancy carries a 25 percent chance of the child inheriting both pathogenic copies and being affected by the condition.