DNA polymerase is an enzyme in eukaryotic cells whose function, in part, is to catalyze phosphodiester bonds formation between adjacent deoxyribose molecules. Blocking the function of this enzyme would initially block

Addition of nucleotides to form a complementary strand of DNA.

Explanation:

Replication of the genetic material (DNA) is a paramount process that must be undergone by any cell prior to its division. The series of processes that occurs to the DNA molecule during DNA replication is catalyzed by different enzymes with specific functions. However, one of these enzyme callee DNA POLYMERASE catalyzes the main event, which is the synthesis of a complementary strand.

DNA polymerase catalyzes the production of phosphodiester bonds that joins the nucleotides. The enzyme synthesizes a nuceleotide base complementary to the one on the template strand, to eventually form a new DNA strand. Hence, blocking the function of this enzyme is tantamount to blocking the synthesis of a new strand itself.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.