How many chemical components are there in DNA?

 

Question:

How many chemical components are there in DNA?

DNA is made of chemical building blocks called nucleotides. These building blocks are made of three parts: a phosphate group, a sugar group, and one of four types of nitrogen bases. To form a strand of DNA, nucleotides are linked into chains, with the phosphate and sugar groups alternating. The four types of nitrogen bases found in nucleotides are adenine (A), thymine (T), guanine (G), and cytosine (C). The order, or sequence, of these bases, determines what biological instructions are contained in a strand of DNA. For example, the sequence ATCGTT might instruct for blue eyes, while ATCGCT might instruct for brown. The complete DNA instruction book, or genome, for a human, contains about 3 billion bases and about 20,000 genes on 23 pairs of chromosomes.