The Variable Containing Names of Marker Variables field is used to specify the
variable in the
Annotation SAS Data Set that contains the names of the markers from the
Input Genotype SAS Data Set. The input data set is first ordered according to this variable, then both data sets are reordered by any reorder variables. If this variable is
not specified, it is assumed that the order of markers (columns) in the
genotype data set corresponds to the order of the markers (rows) in the
annotation data set.