The way melting curves for homozygotes and heterozygotes are plotted depends on
the base curve you selected for the Difference Plot. In the example above, a homozygote
sample was selected as base curve, resulting in negative melting curves for the
heterozygotes. (This is because heterozygotes melt at a lower temperature than homozygotes.)
If you selected a heterozygote sample as base curve, homozygotes would
appear as positive melting curves in the example shown