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QTDT - Variance Components

Variance components can be used to describe the similarities between individuals in a pedigree. Variance components are specified with the -w (for the null hypothesis) and -v (for the alternative hypothesis) options. Variance components may be combined. For example, to allow for an environmental (e) and a polygenic (g) component under the null hypothesis use the -weg option.

Value  Description
e Non-shared Environment. This represents the environmental effects that are unique to each family member, including measurement error. This component of variance is fitted using the identity matrix.
g Polygenic. These effects are a function of relatedness between family members and may be due to polygenes. This component of variance is fitted using the kinship matrix.
a Additive Major Gene Effect. This represents the additive effect of linkage to a major gene. This component of variance is fitted using pi-hat measure derived from the IBD matrix between relatives. 
t Twin Environment. This represents the environment shared by twins, but not other types of relatives.
c Common Environment. This represents the environment shared by all related individuals.
n Nuclear Family Environment. This represents the environment shared by all members of a nuclear family.
d Dominance Major Gene Effect. This represents the dominance effects of linkage to a major gene, and is fitted using the probability of sharing two alleles between relatives.


 
 

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