ID variables ;

The ID statement is required and must contain, in the following order, either of these sequences of IDs:

• the pedigree ID, the individual ID, then the two parental ID variables

• the individual ID, then the two parental IDs

Thus if only three variables are specified in the ID statement, it is assumed that the pedigree identifier has been omitted. The pedigree ID is not necessary if all the individual identifiers are unique. The individual and two parental ID variables can be either numeric or character, but all three must be of the same type. The pedigree variable, if specified, can be either numeric or character regardless of the type of the other three identifiers.