What are chromosomes primarily composed of?

Chromosomes are primarily composed of DNA and proteins. The DNA in chromosomes contains the genetic blueprint necessary for the growth, development, and function of all living organisms. Each chromosome is structured as a long molecule of DNA, which is wrapped around proteins called histones. This combination of DNA and histones enables the efficient packaging of genetic material, ensuring it fits within the nucleus of the cell. The proteins not only help organize and compact the DNA but also play key roles in the regulation of gene expression and DNA replication.

The other components mentioned in the incorrect options do not form the structure of chromosomes. RNA and proteins, while critical for cellular functions including protein synthesis and various regulatory roles, do not constitute the primary structure of chromosomes. Similarly, amino acids and enzymes are involved in numerous biochemical processes but are not structural components of chromosomes. Fatty acids and sugars, while important for cellular energy and metabolism, are unrelated to the composition of chromosomal structure. Thus, the composition of chromosomes as a complex of DNA and proteins is essential for their role in heredity and cellular function.