Question

Describe the hierarchical levels of eukaryotic DNA packaging.

Options

• Linear DNA → Circularisation → Looping → Supercoiling → Nucleoid

• Nucleosome (10 nm) → Solenoid (30 nm) → Loops → Higher-order loops → Metaphase chromosome (700 nm)

• DNA double helix → RNA connector loops → Histone binding → Final compaction

• Nucleosome → Histones → NHC proteins → Chromatin

Answer 1

Eukaryotic DNA packaging follows a hierarchical, multi-level organisation: the DNA double helix (~2 nm) wraps around histone octamers to form nucleosomes (~10 nm); nucleosomes coil into a solenoid structure (~30 nm); the solenoid forms loops anchored by NHC proteins; these loops further condense into higher-order structures; and finally, DNA condenses into metaphase chromosomes (~700 nm), achieving ~10,000-fold compaction overall.