Fig. 4. Results of BglI digestions of the PCR fragments amplified from the DNA of three different regions of the CNS. The top band is the 108 bp wild-type mtDNA fragment. The two lower bands are the 35 and 73 bp fragments derived from mutant mtDNA. A, Regional tissue compared with pooled neuronal isolates. Unmarked lane, Size marker, φX174 digested with HinfI. Lane 1, Uncut; lane 2, inferior olivary nucleus, tissue; lane 3, inferior olivary nucleus, neuronal somas; lane 4, dentate nucleus, tissue; lane 5, dentate nucleus, neuronal somas; lane 6, spinal cord, tissue; lane 7, spinal cord, motor neuron somas; lane 8, MERRF patient’s blood; lane 9, mother’s blood. B, Regional tissue compared with neuropil. Unmarked lane, Size marker, as inA. Lane 1, Dentate nucleus, tissue;lane 2, dentate nucleus, neuropil. C, Regional tissue compared with a single neuron. Lane 1, Cerebellar tissue; lane 2, single Purkinje cell equivalent; lane 3, primers only, no DNA (arrow indicates primer dimer). D, pBluescript II SK as DNA internal marker of digestion withBglI. Unmarked lane, Size marker, 1 kb DNA ladder.Lane 1, Complete digestion; lane 2, uncut. The bottom band is supercoiled DNA; thetop band is relaxed circular DNA.