What are chromosomes primarily made of?

Chromosomes are primarily made of DNA and protein molecules, which form a complex known as chromatin. DNA carries the genetic information essential for the growth, development, and functioning of an organism. The proteins, primarily histones, play critical roles in packaging and organizing this DNA to fit within the nucleus of a cell. These proteins help to condense DNA into a more compact structure, allowing for the orderly segregation of chromosomes during cell division.

The presence of proteins is fundamental in regulating gene expression and ensuring that the DNA is properly replicated and repaired. This combination of DNA and proteins is what allows chromosomes to maintain their structural integrity and perform their necessary functions during cell division and throughout the cell cycle. The other options do not accurately reflect the composition or function relevant to chromosomes.