What are Okazaki fragments and how they are formed?

An Okazaki fragment is a relatively short DNA fragment on the lagging strand (the anti-parallel strand) of a double helix during replication.

The Japanese researcher Reiji Okazaki discovered that the anti-parallel strand (the lagging strand) was not read continuously but in small Okazaki fragments, since this lagging strand always needs new RNA primer. An Okazaki fragment includes an RNA primer and a piece of strand already replicated by DNA polymerase. After the DNA is synthesized, the DNA-RNA duplex is broken down and the released 3 'end can be used as a primer to fill in the missing fragments with DNA. These fragments are then stuck together by the DNA ligase.