What are the small units that make up a DNA strand called?

• A. Amino acids
• B. Nucleotides
• C. Proteins
• D. Chromatids

Answer: (B)

The small units that make up a DNA strand are called nucleotides. Each nucleotide consists of three components: a phosphate group, a sugar molecule (deoxyribose in the case of DNA), and a nitrogenous base (adenine, thymine, cytosine, or guanine). These nucleotides are linked together by covalent bonds between the phosphate group of one nucleotide and the sugar of another, forming the backbone of the DNA strand.

Nucleotides are essential for the structure and function of DNA, as they provide the coding system for genetic information. The specific sequence of these nucleotides encodes instructions for building proteins and regulating cellular processes. This sequence is read during transcription and translation, leading to protein synthesis.

In contrast, amino acids serve as the building blocks of proteins, and proteins themselves are composed of long chains of amino acids. Chromatids refer to the replicated forms of a chromosome that are joined together at a centromere during cell division, indicating a different aspect of genetic material organization. Understanding the role of nucleotides is fundamental to grasping how DNA operates at a molecular level within cells.