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Chapter 3
The patterns of single gene
inheritance
Part 2
Dr. Hosseini-Asl; Dentistry; ARUMS; 1391
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Holandric inheritance
Y-linked
Male to male inheritance
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Holandric inheritance
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Holandric trait
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Mitochondrial inheritance
• Maternal inheritance
• Cytoplasmic inheritance
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Mitochondrial inheritance
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• Homoplasm
• Heteroplasm
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• Sex-influenced traits
• Sex-limited traits
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Coefficient of inbreeding (f, r)
 In population genetics, Sewall Wright's coefficient of relationship or coefficient of relatedness
or relatedness or r is a measure for the level of consanguinity between two given individuals.
 The coefficient of inbreeding is calculated for a single individual, and is a measure for the
amount of pedigree collapse within that individual's genealogy.
 The coefficient of correlation as defined by Wright (1922) is derived from the definition of the
coefficient of inbreeding f as defined in Wright (1921).
 The purpose of such a coefficient is to express the likelihood of effects due to inbreeding to
be expected based on a known pedigree (i.e. a fully documented genealogy e.g. due to a
fixed system of breeding). The coefficient introduced by Wright (1921) expresses the
expected percentage of homozygosity arising from a given system of breeding.
 For a given gene with dominant and recessive variants A and a, a random-bred stock will be
50% homozygous (25% AA and 25% aa), while a closely inbred population will be 100%
homozygous (100% AA or 100% aa). The coefficient of inbreeding f is thus designed to run
from 0 for an expected 50% homozygosis to111 for an expected 100% homozygosis, f=2h-1,
where h is the chance of finding homozygosis in this gene.
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