i.b.d.: identical by descent

Consider relatives A and B

What is the probability that for any gene the alleles are i.b.d.?

Probability | # identical |
---|---|

$c_2$ | both |

$c_1$ | one |

$c_0$ | neither |

$c_2 + c_1 + c_0 = 1$

$a= 1 + \delta a + e$

From Haldan and Jayacar(1962) tables of r (coefficient of relationship) are presented.

*f*: coefficient of relationship or of inbreeding; the probability that if A has produced a gamete carrying a rare gene, the first tested gamete of B will carry the same gene.

$\phi$ is for sex linked genes in gametes

For diploid genotypes F and $\Phi$ are used

Relation | Symbol | Converse | f |
F | $\phi_{11}$ | $\phi_{12}$ | $\phi_{21}$ | $\phi_{22}$ | $\Phi$ |
---|---|---|---|---|---|---|---|---|---|

Degree 1 | |||||||||

Parent | Child | $\frac{1}{4}$ | 0 | 0 | $\frac{1}{2}$ | $\frac{1}{2}$ | $\frac{1}{4}$ | 0 | |

Degree 2 | |||||||||

Mother’s Parent | Daughter’s Child | $\frac{1}{8}$ | 0 | $\frac{1}{2}$ | $\frac{1}{4}$ | $\frac{1}{4}$ | $\frac{1}{8}$ | 0 | |

Father’s Parent | Son’s Child | $\frac{1}{8}$ | 0 | 0 | 0 | 0 | $\frac{1}{4}$ | 0 | |

Maternal half sib | W | S | $\frac{1}{8}$ | 0 | $\frac{1}{2}$ | $\frac{1}{4}$ | $\frac{1}{4}$ | $\frac{1}{8}$ | 0 |

Paternal half sib | H | S | $\frac{1}{8}$ | 0 | 0 | 0 | 0 | $\frac{1}{4}$ | 0 |

Full sib | M | S | $\frac{1}{4}$ | $\frac{1}{4}$ | $\frac{1}{2}$ | $\frac{1}{4}$ | $\frac{1}{4}$ | $\frac{3}{8}$ | $\frac{1}{2}$ |