Final answer:
DNA polymerase adds nucleotides to the 3'-OH end of the primer, which is a short strand of RNA synthesized by primase. This allows the DNA strand to grow.
Step-by-step explanation:
DNA polymerase adds nucleotides to the 3'-OH end of the primer to start the growing dsDNA chain. The primer is a short strand of RNA that is synthesized by an enzyme called primase. Primase creates the RNA primer against a DNA template, and then DNA polymerase adds new deoxynucleotides to the 3' end of the primer, extending the DNA strand.