Final answer:
DNA polymerase I Klenow fragment is not used for DNA sequencing; it is used for nick translation, digesting protruding 3'-overhangs, and filling-in at recessed 3'-ends.
Step-by-step explanation:
DNA polymerase I Klenow fragment is not used for DNA sequencing. The Klenow fragment of DNA polymerase I is used for various purposes in molecular biology, such as nick translation, digesting away protruding 3'-overhangs, and filling-in DNA at recessed 3'-ends. However, it is not typically used in DNA sequencing protocols.
In DNA sequencing, specifically the Sanger sequencing method, the key to terminating DNA synthesis is the inclusion of dideoxynucleotides, not the action of the Klenow fragment. These dideoxynucleotides lack the necessary 3'-hydroxyl group required for forming phosphodiester bonds, effectively stopping the extension of the DNA chain. The role of DNA polymerase in DNA sequencing is typically fulfilled by other polymerases that are specially optimized for the sequencing reaction.