What is a chromosome?

A chromosome is a structure found in the nucleus of eukaryotic cells that is made of DNA and proteins. It serves to organize and package the genetic material, which contains genes responsible for hereditary traits. Chromosomes ensure that DNA is accurately replicated and distributed during cell division. Each chromosome carries a specific set of genes that determine various biological functions and characteristics of an organism.

In contrast, the other options describe different cellular components. The cell membrane is a protective barrier that regulates what enters and exits a cell. RNA molecules are vital for various processes including protein synthesis, but they do not represent the structure that contains genes. Proteins, on the other hand, are functional molecules that perform a vast array of tasks in the cell but are not involved in the storage of genetic information like chromosomes are. Thus, the choice describing chromosomes accurately captures their essential role in genetics and cellular organization.