Explanation of the SVLM test. Biallelic SNP genotypes (AA, AB, BB) are presented on the X-axes. The B allele is in interaction with some factor. This interaction increases the variance of the trait when the number of B alleles present in the genotype increases. (A) Relation between the genotype and the value of the trait (B) Relation between the genotype and the squared residuals of the trait, conditional on the genotype.