What are chromosomes composed of?

Chromosomes are primarily composed of DNA molecules, which carry the genetic information necessary for the growth, development, and functioning of an organism. DNA (deoxyribonucleic acid) is a long polymer made up of repeating units called nucleotides, which contain a sugar, a phosphate group, and a nitrogenous base. In eukaryotic cells, DNA is tightly coiled and packaged with proteins called histones to form the structure of chromosomes. This structure not only protects the DNA but also plays a role in regulating gene expression and DNA replication.

While proteins, RNA molecules, and amino acids are essential components of cellular functions and structures, they do not make up the chromosomes themselves. Proteins play a key role in the structure and function of cells, RNA molecules are crucial for protein synthesis and gene expression, and amino acids are the building blocks of proteins. However, when discussing the composition of chromosomes specifically, DNA as the primary molecule is the correct answer.