Fundamentals of Molecular Biology - V.I. Rezyapkin 2009

Nucleic Acids
Organization of Eukaryotic DNA

The length of a eukaryotic DNA molecule is many times greater than the size of The Cell. To ensure that various biological processes can proceed properly, it must be packaged accordingly. There are several levels of DNA compaction.

1. Naked DNA - represents a double helix with a diameter of 1.8 nm:

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Such DNA exhibits hypersensitivity to DNases, which are Enzymes that hydrolyze phosphodiester bonds.

2. Beads-on-a-string:

a) DNA (about 160 bp) makes two turns around the nucleosome core;

b) the nucleosome contains two molecules of each of the H2A, H2B, H3, and H4 Histones, meaning it consists of an octamer of eight molecules;

c) the DNA length between nucleosomes (linker DNA) is about 60 bp.

3. 30 nm - Chromatin fiber:

This Structure is formed As a result of the interaction between the H1 histone and the linker DNA, with a diameter of 30 nm.

4. A series of loop domains. DNA-binding Proteins take part in The formation of this structure by organizing 30-nm fibers consisting of 20,000 to 100,000 nucleotide pairs into loops:

5. Metaphase chromosome:

This structure is formed during mitosis. In the chromosome, DNA is at its most compact state.



Last update: 12/08/2026

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