DNA Packaging

[CrazCo]

All the terms are confusing me. How do histones, nucleosomes, solenoids and looped domains all fit into DNA packaging?

 

:S:S

[aboyliketim]

Hi I think I can try helping you with this, we learnt this in school last year!

 

So in eukaryotes, various proteins fold and condense into fine DNA thread. There's a multilevel packing system, and finally you get a highly compact linear chromosome.

 

There're 5 stages in general:

1. Short region of DNA double helix

2. Nucleosomes: "beads on a string", 10nm chromatin fibre

3. Solenoid of packed nucleosomes: 30-nm fibre

4. Looped domains: 300nm chromatin fibre

5. Entire mitotic chromosome

 

So generally 1 'winds around' nucleosomes to form beads on a string. The 'beads on a string' are then packed into a solenoid, which is then folded into long loops.

The long loops are then attached to a network of nonhistone scaffolding proteins, and later condenses further into the entire mitotic chromosome.

 

If you still need help with this, feel free to tell me/pm me, I can send you a scan of my notes on this! Its not the best handwriting, but legible, with illustrations and more details, done while I was revising for my exams last year.

 

Cheers!

[biome]

well, most of the things are describes by aboyliketim very well....its really amazing how such long dna is packaged into the cell..for a human cell, its almost a metre long, and with several folds of packaging its very well places into a aprox 10micrometre cell size..

while learning this , its interesting to imagine what happens when DNA replication has to occur and the enzymes have to really open up the DNA...

one of the best books that describes as well as provides animations is Molecular Biology of the Gene by Watson and others (i think 8th edition), If you come accross this book in the library, then worth to read it

[DeltaScience]

Hi! well the explanation from aboyliketim is really good and accurate, I just wanted to share this video that I found in youtube wich I'm sure will give you a better perspective about this topic, just take into consideration of what aboyliketim told you and search for the structures!.

 

 

I'm not the author of this video, no credits associated with me.

 

Regards!

Edited January 25, 2011 by DeltaScience