Biochemistry. Nucleic acids occur in every living cell and are the repository of genetic information and the most important substances in protein biosynthesis. High molecular weight polymers containing a mixture of purine and pyrimidine nucleotides chained together by phosphodiester bonds. In DNA, (deoxyribonucleic acid) the sugar group is deoxyribose and the bases of the nucleotides adenine, guanine, thymine and cytosine. RNA, (ribonucleic acid) has ribose as the sugar and uracil instead of thymine.