# Autosomal Recessive Inheritance Risk Calculator Compute per-child and cumulative autosomal recessive disease risk from parental statuses (carrier / affected / non-carrier / unknown via population carrier rate), including the 2/3 carrier rule. Derived from Griffiths, Hartl & Clark 2007, StatPearls. Educational use only. > Canonical page: https://elysiatools.com/en/tools/autosomal-recessive-risk - **Category:** Education - **Keywords:** autosomal recessive, recessive inheritance risk, carrier risk calculator, genetic risk, carrier frequency, cystic fibrosis inheritance, recurrence risk, two-thirds carrier probability, mendelian inheritance, genetics counseling tool ## Overview The Autosomal Recessive Inheritance Risk Calculator estimates the affected-child risk for two parental genotype statuses and the cumulative chance that at least one of a specified number of children is affected. It supports carrier, affected, not-a-carrier, and unknown statuses, using a population carrier rate for unknown parents. Educational use only. ## Inputs - **Parent 1 Status** (select): Genotype status of the first parent. - **Parent 2 Status** (select): Genotype status of the second parent. - **Population carrier rate** (number): Population carrier frequency c used when a parent's status is unknown (P(Aa) = c, P(aa) = c²). - **Number of children** (number): Number of children for the cumulative at-least-one-affected risk. - **Decimal Places** (number) ## When to use - Estimate the per-child risk for an autosomal recessive condition from known parental statuses. - Use a population carrier rate when one parent's genotype status is unknown. - Calculate the cumulative probability that at least one of multiple children is affected. ## How it works - Select a status for each parent: carrier (Aa), affected (aa), not a carrier (AA), or unknown. - Enter the population carrier rate when a parent's status is unknown, along with the number of children. - The calculator combines each parent's probability of transmitting the recessive allele to determine the per-child affected risk. - It reports the per-child result and the cumulative risk for at least one affected child using 1 − (1−r)^n; for two carriers, it also applies the 2/3 carrier probability among unaffected children. ## Use cases - Teaching Mendelian inheritance with carrier, affected, and non-carrier genotype combinations. - Exploring how an unknown partner's population carrier rate changes recurrence risk. - Comparing single-child risk with the chance that at least one child is affected across several children. ## Frequently asked questions ### What parental statuses does the calculator support? It supports carrier (Aa), affected (aa), not a carrier (AA), and unknown. ### What does the population carrier rate mean? It is the value c used to estimate an unknown parent's status, with P(Aa)=c and P(aa)=c². ### What is the risk when both parents are carriers? Each child has a 25% affected risk, a 50% carrier probability, and a 25% probability of being a non-carrier. ### What is the 2/3 carrier rule? For two carrier parents, an unaffected child has a 2/3 probability of being a carrier. ### Is this calculator a substitute for genetic counseling? No. It is intended for education and does not replace professional genetic counseling. ## Related tools - [PCR Annealing Temperature Calculator (Ta = Tm − 5°C)](https://elysiatools.com/en/tools/annealing-temperature-calculator): PCR Ta by the simple rule (lower primer Tm − 5°C) or the Rychlik 1990 formula (0.3·Tm_primer + 0.7·Tm_product − 14.9), with a ±3°C gradient window and primer-Tm mismatch warning. 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