Question

Select all the examples of evidence for nucleosome supercoiling.

A. A 300 Å fiber with 6 nucleosomes per turn is visible using electron microscopy.
B. Removal of some histone H1 causes the 300 A to unwind to 100 A.
C. Using electron microscopy, nucleosomes appear like beads with a diameter of 100 Å.
D. Metaphase chromosomes from which histones have been extracted still maintain an X-like shape.
E. Loops of chromatin are visible using electron microscopy.

Answer 1

A. A 300 Å fiber with 6 nucleosomes per turn is visible using electron microscopy.

C. Using electron microscopy, nucleosomes appear like beads with a diameter of 100 Å.

E. Loops of chromatin are visible using electron microscopy.

Step-by-step explanation:

The nucleosomes are the key subunits of the chromatin, and they consist of two turns of DNA wrapped around a set of two copies each of the H2A, H2B, H3, and H4 histone proteins (i.e. an octamer of histones), which are connected by linear DNA and H1 histones. A zig-zag array of the nucleosomes form a 100 Angstrom (10-nm) nucleosome fiber. Subsequently, multiple histones are packaged into a 30-nanometer (300 Angstrom) fiber named solenoid. The chromatin loops are finally condensed into higher-order structures, which form chromosome sections (300 nm) and chromosome arms (700 nm), respectively.