Sanger sequencing is a method where the DNA is replicated but it adds only one nucleotide to the mix each time. This means that you end with several fragment of the DNA chain that end in that nucleotide, for example, adenine. Theprocess is repeated awith each nucleotide.
After the replication, the DNA is observed in an electrophoresis gel, where the smaller fragments move faster and further, while the bigger fragments remain near the loading point.
We can read the gel from bottom to top to know the sequence of the DNA segment, in this case it would be as fllows: (5' to 3')
5' - CAG GAT ATT GCC GAG GCA TGG ATC CGC CTA AGC TGA CTG GAG AAA ATT CTG ATT AGC GTA TGA ATA - 3'
And the complementary sequence (3' to 5') would be:
3' - GTC CTA TAA CGG CTC CGT ACC TAG GCG GAT TCG ACT GAC CTC TTT TAA GAC TAA TCG CAT ACT TAT - 5'