Dna polymerase catalyzes the joining of a nucleotide to a growing dna strand. What prevents this enzyme from catalyzing the reverse reaction?

hydrolysis of pyrophosphate (PPi) to inorganic phosphate (Pi) + Pi.

Explanation:

The process of DNA replication involves the enzyme called DNA polymerases, which is responsible to synthesize DNA in the 5' to 3' direction with the help of a template.

DNA polymerase are responsible for the addition of nucleotides one by one to the growing DNA chain. DNA polymerase catalyze the formation of a phosphodiester bond between the nucleotides and the pyrophosphate (PPi) group in the terminal primary nucleotide. PPi must be hydrolyzed to form inorganic phoshate (Pi) + Pi by accompanying pyrophosphatase enzymes, which ensure that the free energy change of the DNA synthesis cycle is negative and can continue in the forward direction.

Hence, the hydrolysis of pyrophosphate (PPi) to inorganic phosphate (Pi) + Pi allows the forward movement of DNA strand.