Question

What is the diameter of the nucleosome fibre (beads-on-string structure)?

Options

• Approximately 300 nanometres

• Approximately 10 nanometres

• Approximately 2 nanometres

• Approximately 30 nanometres

Answer 1

The nucleosome fibre, often visualized as a 'beads-on-a-string' structure in electron microscopy, has a diameter of approximately 10 nanometres. This represents the first level of higher-order chromatin organisation beyond the DNA double helix (~2 nm) and is the fundamental repeating unit visible at this magnification.