X Recessive Son Risk

Compute an X-recessive carrier-mother son-risk model with explicit carrier prior, birth sex probability, and penetrance.

Description

A simple X-recessive carrier-mother model separates risk conditional on a son from risk per birth.

A simple X-recessive carrier-mother model separates risk conditional on a son from risk per birth. Penetrance affects whether a transmitted variant is expressed.^[1]

Compute an X-recessive carrier-mother son-risk model with explicit carrier prior, birth sex probability, and penetrance.

When to use X Recessive Son Risk

Use this for the following task: Compute an X-recessive carrier-mother son-risk model with explicit carrier prior, birth sex probability, and penetrance.

Prepare the observed records or explicit model parameters requested below. Keep probabilities as fractions and paired records aligned.

How to use X Recessive Son Risk and understand its results

Prepare the observed records or explicit model parameters requested below. Keep probabilities as fractions and paired records aligned.
Enter motherCarrierProbability, maleBirthProbability, penetranceFraction using the field table, then run the tool.
Read affectedGivenSonProbability, affectedSonPerBirthProbability. Interpret flags, units, ordering and placeholder values using the rules below.
Review any reported issue or failed check, correct the supplied values when appropriate, and verify the result in its intended context.

Input field	Meaning	Value type and bounds	Requirement
motherCarrierProbability	Mother carrier probability	number	Required
maleBirthProbability	Male birth probability	number	Required
penetranceFraction	Penetrance fraction	number	Required

Supply all three probabilities in [0,1]. Apply the one-half carrier transmission model, then multiply by the male-birth probability for the unconditional result.^[2]

givenSon = carrierPrior × 0.5 × penetrance; perBirth = givenSon × maleBirthProbability

This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.

Output field	Meaning	Value type
affectedGivenSonProbability	Affected given son probability	number
affectedSonPerBirthProbability	Affected son per birth probability	number

json

{
  "input": {
    "motherCarrierProbability": 1,
    "maleBirthProbability": 0.5,
    "penetranceFraction": 1
  },
  "output": {
    "affectedGivenSonProbability": 0.5,
    "affectedSonPerBirthProbability": 0.25
  }
}

Limitations and assumptions

This is a stated inheritance model, not a personalized risk assessment. Other maternal genotypes, de novo variants and sex-chromosome exceptions are excluded.

The tool evaluates supplied observations or a declared model. It does not establish the biological cause of an observed pattern. Malformed requests produce input errors. A successfully evaluated request can still contain false flags, empty result lists or a result outside the supplied threshold; those outcomes have the meanings stated above.

Alternative or Complementary methods

Choose Two Generation Bayes Update for this operation: Apply sequential family-evidence likelihood ratios from two generations to a prior risk. For a complementary task, use Genotype Carrier Penetrance for this operation: Estimate observed penetrance among assessed carriers of a defined genotype.

Further background: Inheritance patterns.

References

Inheritance patterns — National Library of Medicine
X Recessive Son Risk — tool.io

Similar or alternative tools

Two Generation Bayes Update
Apply sequential family-evidence likelihood ratios from two generations to a prior risk.
Genotype Carrier Penetrance
Estimate observed penetrance among assessed carriers of a defined genotype.