Entry courtesy of
The National Human Genome Research Institute (NHGRI)

Nucleotide

One of the structural components, or building blocks, of DNA and RNA. A nucleotide consists of a base (one of four chemicals: adenine, thymine, guanine, and cytosine) plus a molecule of sugar and one of phosphoric acid.

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Dr. Robert Nussbaum, of the National Human Genome Research Institute's Laboratory of Genetic Disease Research, defines nucleotide.