In 1968, Reiji and Tsuneko published their breakthrough findings on Okazaki fragments in " PNAS ".
12.
This enzyme makes discontinuous segments ( called Okazaki fragment s ) before DNA ligase ( violet ) joins them together.
13.
During this process, RNA and DNA primers are removed, allowing the Okazaki fragments to attach to the lagging DNA strand.
14.
Priming occurs once at the origin on the leading strand and at the start of each Okazaki fragment on the lagging strand.
15.
However, at the lagging strand, DNA polymerase ? needs to be continually loaded at the start of each Okazaki fragment.
16.
It is predicted to remove Okazaki fragment RNA primers during lagging strand DNA synthesis and to excise single ribonucleotides from DNA-DNA duplexes.
17.
Further research implicates the supplementary role of proliferating cell nuclear antigen ( PCNA ) to DNA ligase I's function of joining Okazaki fragments.
18.
When the PCNA binding site on DNA ligase I is inactive, DNA ligase I's ability to connect Okazaki fragments is severely impaired.
19.
Thus, a proposed mechanism follows : after a PCNA-DNA polymerase ? complex synthesizes Okazaki fragments, the DNA polymerase ? is released.
20.
In this model, upon reaching a CAR, the cell switches DNA polymerases in a mechanism similar to that used in Okazaki fragment synthesis.
