An individual’s genotype for a marker is considered missing if at least one of the alleles at the marker is missing. Any missing genotypes are excluded from all calculations. However, the individual’s nonmissing genotypes at other loci can be used as part of the calculations. If a child has a missing trait value, then that individual is excluded from the statistical tests; allelic transmission scores can still be calculated for such children. Missing trait values of individuals used only as parents do not affect the analysis. See the following section for information about missing values in the ID variables.