nucleic acid. A nucleic acid is a long molecule made up of smaller molecules called nucleotides. Nucleic acids were discovered in 1868, when twenty-four-year-old Swiss physician Friedrich Miescher isolated a new compound from the nuclei of white blood cells.ucleic acid. A nucleic acid is a long molecule made up of smaller molecules called nucleotides. Nucleic acids were discovered in 1868, when twenty-four-year-old Swiss physician Friedrich Miescher isolated a new compound from the nuclei of white blood cells.