How To Calculate Coefficient Of Relatedness

Coefficient of Relatedness Formula:

\[ r = \left(\frac{1}{2}\right)^g + \left(\frac{1}{2}\right)^h + \cdots \]

Coefficient of Relatedness (r):

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1. What is Coefficient of Relatedness?

The coefficient of relatedness (r) measures the proportion of genes that two individuals share by descent from a common ancestor. It is used in population genetics, evolutionary biology, and kinship analysis to quantify genetic relationships.

2. How Does the Calculator Work?

The calculator uses the path coefficient method:

\[ r = \left(\frac{1}{2}\right)^g + \left(\frac{1}{2}\right)^h + \cdots \]

Where:

\( r \) — Coefficient of relatedness (dimensionless)
\( g, h, \cdots \) — Number of generations for each path connecting two individuals
\( \frac{1}{2} \) — Probability that an allele is transmitted from parent to offspring

Explanation: Each path between two individuals through common ancestors contributes to the total relatedness coefficient. The formula sums the probabilities over all possible paths.

3. Importance of Relatedness Calculation

Details: The coefficient of relatedness is crucial for understanding kin selection, predicting inheritance patterns, studying population structure, and analyzing evolutionary strategies like altruistic behavior.

4. Using the Calculator

Tips: Enter the number of generations for each path as comma-separated values. For example, for full siblings (paths: 2,2), enter "2,2". For parent-child relationship (path: 1), enter "1".

5. Frequently Asked Questions (FAQ)

Q1: What does r = 0.5 mean?
A: r = 0.5 indicates that two individuals share 50% of their genes by descent, typical of parent-child or full sibling relationships.

Q2: How is this different from genetic similarity?
A: Coefficient of relatedness measures shared genes due to recent common ancestry, while genetic similarity can include coincidentally shared genes in a population.

Q3: What are common r values?
A: Parent-child: 0.5, Full siblings: 0.5, Half-siblings: 0.25, Grandparent-grandchild: 0.25, First cousins: 0.125.

Q4: Can r be greater than 1?
A: No, r ranges from 0 (unrelated) to 1 (identical genotypes, like identical twins or clones).

Q5: How do I find all paths in a pedigree?
A: Trace all routes connecting two individuals through common ancestors, counting generations along each path without backtracking.