MCAT Biological and Biochemical Foundations of Living Systems Practice Exam 2025 – Comprehensive All-in-One Guide for Success!

The primary structure responsible for wrapping DNA in eukaryotic cells is histones. Histones are basic proteins that bind to DNA, helping to organize and compact it into a structure known as chromatin. This packaging is essential for several reasons: it allows for the efficient storage of the genetic material within the confines of the nucleus, it protects the DNA from damage, and it plays a crucial role in the regulation of gene expression.

In eukaryotic cells, the DNA is wrapped around histone proteins to form nucleosomes, which resemble 'beads on a string.' Each nucleosome consists of a segment of DNA wound around a core of histone proteins. This arrangement allows for further coiling and folding, resulting in the highly condensed structures seen during cell division.

The other choices listed do not play a direct role in wrapping DNA. Nucleotides are the building blocks of DNA and RNA but do not provide structural support by themselves. Ribosomes are involved in protein synthesis and are not involved in the organization of DNA. RNA polymerase is the enzyme responsible for synthesizing RNA from a DNA template during transcription, rather than influencing the structural organization of DNA. Thus, histones are distinctly responsible for the structural wrapping and compaction of DNA in