Question

My lectures briefly mention it is important to know what is meant by the 10nm and 30nm fibres in regards to the organisation of DNA in chromosomes.
Can someone clarify what is meant by this?

Thanks!

Answer 1

10 nm fibers refers to DNA wrapped around histones.

30 nm fibres refers to histones interacting with each other to form nucleosomes.

Answer 2

So the 30nm fibre is a bundle of 10nm fibres?

Answer 3

Yup.

The DNA wraps around complexes of histones to form nucleosomes. This is the 10 nm fibres which looks like "beads on a string" under an electron microscope. Then the different nucleosomes interact with each other - the DNA between them is carefully condensed - to form the 30 nm fibre.

Then the 30 nm fiber undergoes several further levels of looping and folding to form chromosomes during cell division.

Answer 4

Perfect answer mate, thanks very much.

Answer 5

So if the 10nm fibre is the nucleosome, then does the 30nm fibre have a specific name? Or is it just relaxed chromosome?

Answer 6

I'd simply call it "condensed chromatin" or "condensed DNA" but in general, I can't remember ever coming across a specialised name for it in the literature. Which is not say that it doesn't have a proper name.

Answer 7

Thanks again!

Answer 8

!0 nm fibre is bead on string structure. Nucleosome are placed in line.
30 nm fibre they form helix kind of structure having three nucleosome at each level giving size 10*3= 30nm