Which of the following is NOT a nitrogen base found in DNA?

Lysine is not a nitrogen base found in DNA; this makes it the correct answer. In the context of DNA, the four primary nitrogenous bases are adenine, cytosine, guanine, and thymine. These bases are integral to the structure of DNA, as they form the rungs of the double helix by pairing specifically (adenine with thymine and cytosine with guanine).

Lysine, on the other hand, is an amino acid that plays a crucial role in protein synthesis but does not participate in the composition of DNA. It is important to note that while lysine is a nitrogen-containing compound, it does not serve as a building block of nucleic acids like DNA.

Understanding the distinction between amino acids and nitrogen bases is vital for grasping molecular biology. This helps clarify the structure and function of macromolecules within biological systems, emphasizing the unique roles each component plays.