Which of the following nucleotides is NOT part of DNA?

Uracil is not a part of DNA. In the structure of DNA, the nucleotides consist of four key bases: adenine, thymine, cytosine, and guanine. These bases pair specifically: adenine pairs with thymine and cytosine pairs with guanine, which is critical for the stability and integrity of the DNA double helix structure.

Uracil, on the other hand, is found in RNA, where it replaces thymine as one of the four nucleotide bases. In RNA, adenine pairs with uracil instead of thymine. This distinction between the bases is fundamental to understanding the differences between DNA and RNA in biological systems. Therefore, identifying uracil as the nucleotide that is not part of DNA correctly highlights the unique roles that these nucleotides play in nucleic acids.