Genome-wide two-point VC linkage analysis was performed using SOLAR 1.7.3 [7]. Under the null hypothesis of no linkage, the QTL variance was fixed at zero and was tested against a polygenic model in which the same parameter was estimated from the data using maximum likelihood methods. Adjusted VC analyses considered sex and age as covariates. Adjusted multi-point analysis was performed on chromosomes with sex- and age-adjusted two-point LOD scores > 1.0.
