Mechanism of DNA Replication (Advanced)

[clairebehun]

love the video man

[saguhh00]

Why does this video have dislikes? Are there people who don't believe in DNA?

[ackilla86]

our Creators are THE greatest scientists ever!



[boblee666]

@ackilla86 NO THE GREATEST MATHEMATICIAN.

[vldk29]

Oh, is the green structure the DNA primase?

[RodAGTotoro]

@vldk29 If you're talking about the light green structure that comes and goes leaving a yellow nucleic acid region, then it is, and the yellow thing is the RNA primer.

If you're talking about the green structures like donuts at the end of the "arms" of the complex, then it is no, that's the Beta-clamp.

[vldk29]

Hi,

This may sound a little stupid, but, what happens when the clamp 'associates' with the helicase? Does the helicase allow the clamp to bind to the lagging strand? Also, what is the green structure that temporarily binds to the helicase just before the clamp comes to it?

And another question, does this occur when the primer is added to the lagging strand?

Thank you.

[RodAGTotoro]

@vldk29 Hadn't seen your first question. It's not stupid at all. I'll try to answer it.

:D

The clamp doesn't associate to the helicase, but to the core polymerase (made of an alpha, epsilon and theta subunit), which is shown in purple at the end of the arms. There's a clamp that also associates with the "Clamp Loading Complex" which is the one at the center that gets closer to the helicase and then goes back to its position (light purple).

[RodAGTotoro]

@vldk29 Once the clamp is loaded in the complex, it is in the "open" conformation. The whole complex approaches the helicase where the clamp closes around the DNA laggin' strand and the complex goes back to its extended position. Then the core polymerase of the lagging strand takes the clamp (with the DNA associated to it) and continues the synthesis of DNA untill it fills the space between the new primer and the old okazaki fragment.

[RodAGTotoro]

@vldk29 I guess your last question was asked in my first reply. The light green structure being the primase and the dark green being the clamps. The primase adds a new primer and then dissociates. The clamp closes around the the new template primer, the core polymerase gets the clamp with the DNA associated to it and DNA synthesis keeps on going and going and going on forever. Well... at least until the end of the chromosome is reached.

[qrais]

the holoenzyme complex consist of how many subunits???

[RodAGTotoro]

@qrais It depends on which species and which polymerase are you talking about. In E. coli there are at least 5 polymerases, the one depicted here is the DNA pol 3, which is made up of at least 10 subunits.

E. coli DNA pol 1 is made of 1 subunit and E coli DNA pol II is made of 7 different subunits.

[qrais]

@RodAGTotoro thank you very much for your answer. Thank you.

[adamcolon]

"Numerous components have been deliberately left out to avoid complete confusion" AAAH *brain asplods*

I'm gonna have to watch this another 20 times

[utkanos]

this video proves how potential biochemistry is. Imagine in future there will be nanoscale factories like this

[TheMordyS]

SLOW DOWN!!

[Missfieryfist]

thanks! this is really helpful!!