Molecular Biology | Biochemistry for Medics – Lecture Notes
Benzene (EHC 150, 1993) - INCHEM
The greatest mystery of discontinuous replication was the mechanism of initiation of Okazaki fragment synthesis. In the 1970s, it became increasingly clear that all DNA polymerases always require primers for initiation of their polymerase reaction and that none of them can initiate DNA polynucleotide chain synthesis from only two nucleotides. As synthesis of Okazaki fragments must be initiated frequently during the process of DNA replication, we had no clues as to how to explain the biochemical basis of such events.
Human Brain – Neuroscience – Cognitive Science
When the discontinuous replication model was proposed, DNA polymerase I was the only DNA polymerase enzyme identified in . However, it was soon recognized that the DNA polymerization reaction catalyzed by this enzyme required a primer, a pre-existing short polynucleotide chain. In other words, DNA polymerase I is only capable of adding a nucleotide to the end of a pre-existing polynucleotide chain. For the true initiation of the DNA replication reaction, the existence of another DNA polymerase enzyme that is capable of the synthesis of the polynucleotide chain was anticipated. That is, DNA chain synthesis that can be initiated without requiring a pre-existing polynucleotide precursor. When the cell components were separated into the soluble or membrane fractions under mild conditions, most of the DNA polymerase I activity was recovered in the soluble fraction, but the membrane fraction still contained the discontinuous replication activity.