Perpendicular TGGE in patient no. 2. MtDNA fragment, nt 6504-6923. 5% polyacrylamide gel, silver staining. The typical heteroduplex pattern (two clearly separated heteroduplex bands on the left, two homoduplex bands not clearly separated on the right) indicates the presence of two homologous mtDNA species (wild-type and mutated), which after a cycle of denaturation and renaturation produce hybrids differing in their melting behavior.