Okazaki fragments are short segments of newly synthesized DNA that are formed on the lagging strand during DNA replication. DNA replication is the process by which a cell copies its DNA before cell division so that each daughter cell receives an identical set of genetic information.
During DNA replication, the two strands of the DNA double helix separate and each strand acts as a template for the synthesis of a new complementary strand. The enzyme DNA polymerase is responsible for adding nucleotides to form the new DNA strand. However, DNA polymerase can add nucleotides only in the 5′ → 3′ direction.
Because of this directional limitation, the two strands of DNA are synthesized differently. The leading strand is synthesized continuously in the direction of the replication fork. In contrast, the lagging strand is synthesized discontinuously in small segments because its direction is opposite to the movement of the replication fork.
These short discontinuous segments of DNA formed on the lagging strand are called Okazaki fragments. Each fragment is synthesized separately and later joined together by the enzyme DNA ligase, which connects the fragments to form a continuous DNA strand.
Thus, Okazaki fragments are short DNA segments produced during the process of DNA replication on the lagging strand and are later joined together to complete the DNA molecule.