Question

A nucleosome A. is a regularly repeating structure of DNA and histone proteins. B. has a core of DNA with proteins wrapped around the outside. C. uses only one rype of histone per nuclcosome. D. is separated from a second nucleosome by nonhistone proteins. E. has histones in contact with the major groove of the DNA.

Short answer

Answer: A. "A nucleosome is a regularly repeating structure of DNA and histone proteins."

Step-by-step solution

Reviewing the basics of nucleosomes

A nucleosome is a structural unit of a eukaryotic chromosome, consisting of a length of DNA coiled around a core of eight histone proteins. Nucleosomes play a significant role in the organization of DNA within the cell and the regulation of gene expression.

Analyzing each statement

A. "A nucleosome is a regularly repeating structure of DNA and histone proteins." This statement is correct, as nucleosomes are the fundamental repeating units found in the chromatin, which is responsible for packing the DNA within the cell. B. "A nucleosome has a core of DNA with proteins wrapped around the outside." This statement is incorrect because it is the opposite of the actual structure: nucleosomes have a core of histone proteins with DNA wrapped around them. C. "A nucleosome uses only one type of histone per nucleosome." This statement is incorrect because each nucleosome is composed of multiple types of histones, specifically two copies of each of the four core histones: H2A, H2B, H3, and H4. D. "A nucleosome is separated from a second nucleosome by nonhistone proteins." This statement is partially correct but does not cover the full description of a nucleosome. Nucleosomes are separated by linker DNA, which can associate with other proteins, including nonhistone proteins. E. "A nucleosome has histones in contact with the major groove of the DNA." This statement is incorrect because histones primarily interact with the minor groove of the DNA, while the major groove faces outward and remains accessible for protein binding and regulation.

Selecting the most accurate statement

Based on the analysis of all the statements, the most accurate description of a nucleosome is: A. "A nucleosome is a regularly repeating structure of DNA and histone proteins." This statement emphasizes the nucleosome's repeating, organized structure and its composition of DNA wrapped around histone proteins.