= DNA sequencing
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<DNA sequencing> determines the order of <nucleotide> bases in <DNA>. Sequence data can test molecular rearrangements, as in the <functional plastid-to-nucleus gene transfer experiment>, or support <phylogenetics> after a suitable <sequence alignment>.
An ordered <nucleotide sequence> answers a different question from fragment size. The eight-<nucleotide> strands ACGTTAGC and AACCGGTT have equal lengths and identical counts of <adenine>, <cytosine>, <guanine> and <thymine>, yet different orders. A length-compatible <gel band> therefore cannot identify either strand by itself. <Sanger sequencing> makes length informative by deliberately coupling each stopping position to the identity of its last added <nucleotide>.
That coupling is the beautiful experimental idea: convert an invisible order into a collection of ordered endpoints. <Sanger ladder reading> recovers the newly synthesized strand; <base pairing> and the <reverse complement> then connect that readout to the original template. The distinction also matters when checking a <mutation>: a reliable local <nucleotide sequence> supports a particular molecular change, while its effect on a <phenotype> requires additional evidence.
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