Final answer:
The primosome is a protein complex that initiates DNA synthesis by producing an RNA primer through the enzyme primase. This RNA primer is essential for DNA polymerase to begin adding nucleotides, which starts the replication of both the leading and lagging strands of DNA.
Step-by-step explanation:
The primosome is a protein complex that initiates the synthesis of a DNA strand by conducting the priming reaction. This reaction involves the synthesis of an RNA primer, which is a short complementary sequence of RNA nucleotides. The enzyme primase, a RNA polymerase, is responsible for creating the RNA primer needed for DNA synthesis to begin. This primer provides a free 3'-OH group to which DNA polymerase can add DNA nucleotides, commencing the replication process. The primer is synthesized complementary to the DNA template strand, enabling DNA polymerase III to start adding nucleotides at the 3'-OH end of the primer. This process is essential for both the leading strand, which is synthesized continuously, and the lagging strand, which is synthesized in discontinuous segments known as Okazaki fragments.