In this chapter, we focused on how DNA is replicated and synthesized. We also discussed recombination at the DNA level. Along the way, we encountered many opportunities to consider how this information was acquired. On the basis of these discussions, what answers would you propose to the following fundamental questions? How do we know that DNA synthesis is discontinuous on one of the two template strands?

Key Concepts

DNA Replication

DNA replication is the process by which a cell duplicates its DNA before cell division. It involves unwinding the double helix and synthesizing new strands complementary to each template strand. This process is crucial for genetic continuity and is characterized by leading and lagging strand synthesis, which highlights the discontinuous nature of replication on one strand.

Leading and Lagging Strands

During DNA replication, the leading strand is synthesized continuously in the direction of the replication fork, while the lagging strand is synthesized discontinuously in short segments called Okazaki fragments. This difference arises because DNA polymerase can only add nucleotides in a 5' to 3' direction, necessitating a back-and-forth synthesis on the lagging strand as the fork opens.

Okazaki Fragments

Okazaki fragments are short sequences of DNA nucleotides synthesized on the lagging strand during DNA replication. These fragments are later joined together by the enzyme DNA ligase to form a continuous strand. The presence of these fragments is a key indicator of the discontinuous nature of DNA synthesis on the lagging strand, providing evidence for the overall mechanism of replication.