CofI and Cy2T

Calculation of coefficients of inbreeding

Given a pedigree of known structure, it is possible to calculate the coefficient of inbreeding (F) for a selected person within that family. This represents the probability that any one locus is autozygous by descent from a common ancestor.

A method for estimating F, as well as the coefficient of relationship R for an individual's parents, is described by Young (1). CofI implements this method using a user-friendly Windows interface. A text file specifying the pedigree structure must be provided to the program. This can be quickly generated by hand: alternatively, the accessory program Cy2T can convert a pre-existing Cyrillic pedigree file to the required flat text format.

CofI calculates the following values:

In practice, many inbred families are highly complex in structure and derive from ethnic groups where consanguineous marriage has been practiced for many generations. This means that the apparent founder individuals are not, in fact, unrelated. Nonetheless, this method can estimate a lower limit for the true value of F, based on the specified pedigree.

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Note: these programs require the .NET framework version 2.0 to be installed. (Available through Windows Update.)

1. Young, I.D. Introduction to Risk Calculation in Genetic Counseling, 3rd Ed., Oct. 2006, ISBN 978-0195305272.