Which statement best describes a nucleosome?

Which statement best describes a nucleosome?

• A. A Unit of Chromatin Consisting of a DNA Wrapped Around Histone Proteins
• B. An Enzyme That Unwinds DNA
• C. A Ribosomal RNA Gene
• D. A Segment of Membrane Protein

Answer: (A)

Nucleosomes are the basic units of chromatin where DNA is tightly wrapped around histone proteins. Specifically, about 146 base pairs of DNA wind around a histone octamer composed of two each of the histone proteins H2A, H2B, H3, and H4, forming the nucleosome core. A stretch of DNA called linker DNA connects successive nucleosomes, and the linker-associated histone H1 helps stabilize this structure. This arrangement compactly packages DNA and also controls access to genetic information, influencing which genes can be read or quieted at any given time. So, the statement that describes a nucleosome is that it is a unit of chromatin consisting of DNA wrapped around histone proteins. The other options describe entirely different molecules or features: an enzyme that unwinds DNA (helicase), a ribosomal RNA gene, or a segment of a membrane protein.

Nucleosomes are the basic units of chromatin where DNA is tightly wrapped around histone proteins. Specifically, about 146 base pairs of DNA wind around a histone octamer composed of two each of the histone proteins H2A, H2B, H3, and H4, forming the nucleosome core. A stretch of DNA called linker DNA connects successive nucleosomes, and the linker-associated histone H1 helps stabilize this structure. This arrangement compactly packages DNA and also controls access to genetic information, influencing which genes can be read or quieted at any given time.

So, the statement that describes a nucleosome is that it is a unit of chromatin consisting of DNA wrapped around histone proteins. The other options describe entirely different molecules or features: an enzyme that unwinds DNA (helicase), a ribosomal RNA gene, or a segment of a membrane protein.