Note: Cast
Act I: Initiation:
Once upon a time, there was a DNA that felt that it was time to replicate. He was very old so he enlisted the help of the younger generation.
First, a replication fork is to be formed to separate the strands. This is done by Helicase. He untwistes a section of DNA, then he pulls apart the strands easily because of the weak hydrogen bonds. But he realized that he could not hold the strand apart by himself, so he called upon his buddy, Single-strand binding proteins, who specializes in this job.
While this was happening Old man DNA complained that other parts of his structure became too tight. So Gyrase comes in to release the tension.
Then finally, the synthesis of the daughter strands can begin.
Act II: Elongation:
Since the DNA has been split into 2 strands and each runs anti-parallel to each other. And the new daughter strand is to be synthesised in a 5'-> 3' direction. The 2 daughter strands needs to be formed, each one in the opposite direction of the Old man DNA stand, or template. And depending on whether it is forming towards the fork or away, it is a different process.
Leading strand (towards the fork):
First, RNA primase builds a small RNA segment called RNA primer. Then DNA polymerase III adds nucleotides to the RNA primer continuously.
Things are not so easy for the Lagging strand (away from the direction of fork opening):
The daughter strand is synthesized discontinuously, in sections, where it also starts with a RNA primase, RNA primer, and DNA polymerase III. This is called an Okazaki fragment.
But that's not all, when the Okazaki fragment runs into the RNA primer of another Okazaki fragment in front of it, in comes DNA polymerase I to replace the RNA neucleotides with DNA.
Act III: Termination:
And finally DNA ligase, AKA the Glue man, who's been called in by the youngsters and waiting while this is all taking place, can join the Okazaki fragments. As well Polymerase I & DNA Polymerase II proofreads and repair errors.
