What structure do coiled nucleosomes form?

What structure do coiled nucleosomes form?

• A. Coiled nucleosomes form 30 nm-thick chromatin fibers.
• B. DNA condenses into 70 nm filaments.
• C. Chromatin remains as beads on a string at 2 nm.
• D. Chromatin forms lipid rafts.

Answer: (A)

Nucleosomes coil into a 30 nm chromatin fiber. The basic unit—the nucleosome—shapes a 10 nm beads-on-a-string strand, with DNA wrapped around histone cores. When this 10 nm fiber is drawn together, histone interactions, aided by the linker histone H1, pack neighboring nucleosomes into a thicker, about 30 nm fiber. This higher-order structure lets the long DNA fit inside the nucleus while still allowing regulatory access through remodeling and partial unfolding. The other descriptions describe either the uncondensed form (the 2 nm DNA double helix beads-on-a-string) or unrelated concepts, so they don’t match the organized 30 nm chromatin fiber formed by coiling nucleosomes.

Nucleosomes coil into a 30 nm chromatin fiber. The basic unit—the nucleosome—shapes a 10 nm beads-on-a-string strand, with DNA wrapped around histone cores. When this 10 nm fiber is drawn together, histone interactions, aided by the linker histone H1, pack neighboring nucleosomes into a thicker, about 30 nm fiber. This higher-order structure lets the long DNA fit inside the nucleus while still allowing regulatory access through remodeling and partial unfolding. The other descriptions describe either the uncondensed form (the 2 nm DNA double helix beads-on-a-string) or unrelated concepts, so they don’t match the organized 30 nm chromatin fiber formed by coiling nucleosomes.