Final answer:
In Sanger sequencing, the further development of a DNA strand is prevented by the addition of ddNTPs (dideoxynucleotides).
Step-by-step explanation:
Sanger sequencing is a method used to determine the sequence of DNA. In this method, the further development of a DNA strand is prevented by the addition of ddNTPs (dideoxynucleotides), which lack a hydroxyl group (-OH) at the site where the next nucleotide would attach. When a ddNTP is incorporated into the growing DNA strand, it terminates the replication process.