Exactly why, in Sanger DNA sequencing, do dideoxynucleotides halt the replication process.?

Question

Exactly why, in Sanger DNA sequencing, do dideoxynucleotides halt the replication process.?

Answer 1

It means that the 3' hydroxyl group of the ribose is missing, so that the 5' phosphate of what would be the next base cannot be esterified to it.  (The other oxygen mentioned in the first post has nothing to do with halting DNA replication and is missing from all deoxynucleotides).

Answer 2

The "dideoxy" part means that two sticking-off oxygens are missing.  The next nucleotide has nowhere for its phosphate to attach to.  So nothing can be added.