See Box 1, viz:
QT:{{”
Box 1 Statistical model used in the GREML approach to estimate hS2NP The statistical model used by GREML can be described in its simplest form as y = Wu + e
where y is an n x 1 vector of standardized phenotypes with n equal to the sample size, W = {wij} is an n x m standardized SNP genotype matrix where m is the number of SNPs, u = {ui} is an m x 1 vector of the additive effects of all variants when fitted jointly in the model, u ~ N(0,Iσ2) with I being an identity matrix, u and e is a vector of residuals, e ~ N(0,Iσ2). An equivalent model is….
y=g+e
g ~ N(0,A…)
A=W W’
In practice, A is called the SNP-derived genetic (or genomic) relationship matrix (GRM) and is estimated from the SNP data. The estimate …from GREML can be described as the estimated variance explained by all the SNPs (mσu) or equivalently as the estimated genetic variance by contrasting the phenotypic similarity
between unrelated individuals to their SNP-derived genetic similarity “}}
https://www.nature.com/articles/ng.3941
Yang, J., Zeng, J., Goddard, M. E., Wray, N. R., & Visscher, P. M. (2017). Concepts, estimation and interpretation of SNP-based heritability. Nature Genetics, 49(9), 1304–1310.
https://doi.org/10.1038/ng.3941
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