Marker types in an autotetraploid genotype. Markers A, B, C and D are dominant markers. A, B and C are simple dose (simplex) and D is in double dose (duplex). A and B are linked in coupling phase, A and C or B and C are linked in repulsion phase. Loci E and F show codominant alleles in simple or double dose. A null allele is represented for locus E.