In terms of function, what do chromosomes contain?

Chromosomes contain a long DNA molecule coiled with proteins, which is essential for several key functions in a cell. This structure allows for the efficient packaging of DNA within the nucleus of eukaryotic cells. The DNA in chromosomes not only carries genetic information necessary for the development, functioning, and reproduction of organisms, but it is also organized in such a way that facilitates access to specific genes during processes like transcription and replication. The proteins associated with the DNA, primarily histones, play a critical role in regulating these processes, as they help in the condensation of the DNA and aid in the structural integrity of the chromosome.

The other options do not accurately describe the full scope of what chromosomes contain. A single gene only represents a small portion of what a chromosome comprises. Multiple alleles are variations of a single gene and do not encapsulate the entirety. Non-coding DNA, while present in chromosomes and essential for various regulatory functions, is only part of the overall structure and function of chromosomes, which includes coding regions as well.