A nucleotide consists of: a nitrogenous base, a sugar, a phosphate group. What are the three fundamental building blocks of dna: nitrogenous base, 5-carbon sugar, phosphate group. The sugar phosphate backbone is around the outside of a double stranded molecule with nitrogenous bases in the middle. Name the 4 different nitrogenous bases: thymine, adenine, cytosine, guanine. Different sequences of the 4 possible nucleotides make up the different genetic code of every living organism. Suppose that 22% of an organism"s genome is the nucleotide guanine (g). The phosphate group in a single nucleotide is attached to the ____" carbon atom of the sugar. ****the strands of dna run in an antiparallel manner. The phosphate group in a single nucleotide is attached to the 5" carbon atom of the sugar. Adjacent nucleotides are linked phosphate to 3" carbon atom--- this forms the backbone.