DNA packaging

Organisation of DNA in eukaryotes

This section includes part of the IB topic 7.1:

Structure and function of nucleosomes.
Supercoiling of DNA into chromatin fibres and chromosomes
Molecular visualization of nucleosomes
Non-coding DNA

What are nucleosomes?

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Molecular visualization of nucleosomes

A model of DNA packaging:

The average size of a chromosome is 5 micrometers, but the length of the DNA molecule inside it, is about 5 cm long. How are 5 cm of a double stranded DNA helix compacted into a 5 cm long chromosome? The answers is amazing: nucleosomes and supercoiling of chromatin fibers!

Nucleosomes also play a role in DNA expression.

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Non-coding DNA

Only about 1.5% of the human DNA contains genes.

Introns are examples of non-coding DNA with no defined function.

DNA promoter are examples of non-coding DNA with a function.

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