Why Do Ddntps Stop Dna Synthesis?

Because DdNTPs have a hydrogen molecule (-H) instead of a hydroxyl group (-OH) attached to the 3'-C of its deoxyribose, it cannot bind to any incoming nucleotides. Therefore, addition of DdNTPs during DNA replication can be used to terminate the synthesis reaction.

Why does DNA synthesis stop when a ddNTP is incorporated into the growing DNA strand?

If the added nucleotide is a "dideoxynucleotide" (Figure 6.29), the 3' end of the growing strand will now have an H, rather than an OH. This will prevent any additional nucleotides from being added on; i.e., in vitro DNA synthesis will stop at this point.

How does a ddNTP terminate DNA synthesis?

When a ddNTP is incorporated into a chain of nucleotides, synthesis terminates. This is because the ddNTP molecule lacks a 3' hydroxyl group, which is required to form a link with the next nucleotide in the chain.