- Occurs in the nucleus during the S phase of the cell cycle.
- It is an autocatalytic function of DNA.
- It occurs in a semi-conservative manner.
|Sequence of base pairs in the genome where DNA replication begins. A Nick is created.|
|Helps in unwinding the two strands by breaking hydrogen bonds.|
|Helps in relieving tension caused due to unwinding.|
Single stranded binding proteins
|Prevents reannealing of the two strands.|
|Y-shaped fork formed due to the separation of the two strands.|
|forms the RNA primer at the ORI.|
|Short strand of RNA formed at ORI as DNA polymerase III requires a free OH group at 3′ end to add nucleotides.|
|The nucleotides are high energy compounds present in triphosphate form, they act as the substrate for the new strand and also provide energy to form hydrogen bonds between nitrogenous bases.|
|Addition of nucleotides and it always occurs in 5′→3′ direction.|
DNA polymerase III
|Needed to form the new strand. Shows polymerization in 5′→3′ direction and exonuclease activity in 3′→5′ direction.|
Leading and Lagging strands
|3′→5′ strand is the leading strand as the new strand starts forming as the two strands separate. 5′→3′ strand is lagging strands as the new strand starts forming only after a short part of DNA has opened up.|
Continuous and Discontinuous
|The new strand is formed in a continuous manner in the leading strand and in a discontinuous manner in the lagging strand.|
|Short fragments formed on the lagging strand.|
DNA polymerase I
|Shows exonuclease and polymerization activity. Removes RNA primer and adds deoxyribonucleotides in its place.|
|Helps in joining of Okazaki fragments.|