Final answer:
DNA sequencing techniques, specifically the chain termination method, are used to determine the base sequence of DNA fragments. After sequencing, the fragments are separated by size using electrophoresis, and a computer analyzes the data to reassemble the entire DNA sequence.
Step-by-step explanation:
The actual base sequence of DNA fragments is determined by B) DNA sequencing techniques. In particular, the chain termination method, also known as Sanger sequencing, is a common technique used. This method involves cutting the DNA into fragments, which are then sequenced using dye-labeled dideoxynucleotides that terminate chain elongation. The resulting DNA fragments vary in length and are separated by electrophoresis, typically on a polyacrylamide gel. Each fragment's migration speed through the gel is dependent on its size, with smaller fragments moving faster.
After electrophoresis, the fragments are detected using a fluorescent dye or by autoradiography if radioactive labels were used during the sequencing reactions. A computer then analyzes these fluorescent or radioactive signals in order to determine the sequence of bases. Overlapping sequences are used to help reconstruct the entire DNA sequence from the individual fragments.