Question

Nucleosome is

• A. Satellite DNAs
• B. Intron interrupted DNA
• C. Negatively charged DNA wrapped around positively charged histone octamer
• D. Double helix DNA

Answer 1

The correct option is C Negatively charged DNA wrapped around positively charged histone octamer

Part 1: Intron interrupted DNA
Introns are noncoding regions that interrupt the coding regions in a DNA molecule. Every DNA molecule possesses introns. Intron interrupted DNA is not considered as a nucleosome.

Part 2: Double helix DNA
DNA is a double stranded helical molecule which serves as our genetic material. A DNA double helix on its own is not considered as a nucleosome.

Part 3: DNA wrapped around histone core
Nucleosomes are submicroscopic units of chromatin which are about $11nm$ in diameter and $5.7-6nm$ in height. Each nucleosome consists of a positively charged core of 8 histone molecules around which the negatively charged DNA strand is tightly wrapped in $2$ circles. Adjacent nucleosomes are connected by a linker DNA. A typical nucleosome consists of $200$ base pairs of DNA. Nucleosomes on DNA form a ‘beads on string’ appearance, where the nucleosome forms the beads and the linker DNA is seen as the string.


Part 4: Satellite DNA
Satellite DNAs are tandem repeats of $5$ to $1000$ base pairs and occur either as a single copy dispersed through the genome or as closely spaced clusters. These are not considered to be nucleosomes.

Final answer
(c) Negatively charged DNA wrapped around positively charged histone octamer