What type of cell structure are chromosomes made of?

Chromosomes are primarily composed of DNA, which stands for deoxyribonucleic acid. DNA is a molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known living organisms and many viruses. Each chromosome contains a single, long DNA molecule that is tightly coiled and associated with various proteins. These proteins, known as histones, help to package the DNA into a more compact, organized structure. The unique structure of DNA—its double helix shape—allows for the efficient storage of genetic information and the proper transmission of this information during cell division.

In the context of the other options, proteins play a supportive role by helping to stabilize and organize the DNA within chromosomes, but they do not make up the fundamental structure of the chromosome itself. RNA (ribonucleic acid) is involved in protein synthesis and plays a significant role in gene expression but is not a structural component of chromosomes. Lipids are primarily associated with cellular membranes and energy storage, not with the composition of chromosomes. Therefore, the defining component of chromosomes is indeed DNA.