---

Gel image from an automated DNA sequencer

The gel image is a "false colour" representation of 32 DNA sequences. Each lane represents a separate DNA sequencing reaction: to read both strands of DNA, a single individual is sequenced with either forward and reverse primers, in alternate lanes. The sequencing ladder in each lane can be read from bottom to top: the four different coloured bands in each lane correspond to each of four DNA bases: A C G & T.  The computer scans vertically through each lane: each channel is converted to an individual chromatogram for that DNA sequence. [Click here for a detailed animation of fluorescent DNA sequencing: requires Shockwave].

[Sequence analysis of population variation in a PCR-amplified portion of the mtDNA ND3 locus from Harp Seals (Pagophilus). Gel by K.G. Parsons; PCR products by A.-M. Gale; sequencing reactions by R.A.White; technical supervision by H.D. Marshall; paid for by S.M. Carr].