What is the lagging strand synthesized by?

the DNA polymerase during DNA replication.

The lagging strand is one of the two strands of DNA that are being synthesized during DNA replication. It is called the lagging strand because it is synthesized discontinuously in short fragments called Okazaki fragments.

The lagging strand is synthesized in a series of steps. First, the RNA primer is laid down by the primase enzyme. DNA polymerase then elongates the primer by adding complementary nucleotides in the 5' to 3' direction. Since the lagging strand is synthesized in the opposite direction of the replication fork movement, the DNA polymerase must work in short stretches away from the replication fork.

As the DNA polymerase reaches the end of each Okazaki fragment, it displaces the RNA primer and replaces it with DNA nucleotides. The resulting gaps between fragments are filled in by DNA ligase. This process continues until the entire lagging strand is synthesized.

Overall, the lagging strand synthesis is a more complicated process compared to the leading strand synthesis, as it involves more steps and requires the coordination of multiple enzymes to ensure proper replication of the DNA molecule.