in what ways do the structures of dna and rna molecules differ?
DNA vs. RNA. Structurally RNA is different from DNA in consisting of ribose as pentose sugar and Uracil as the pyrimidine group. RNA is not double helix as DNA, but it forms similar helical structures by being wound back due to base pairing. Just as in DNA, the bases are hydrogen bonded in RNA in these helical regions. RNA exists as single helix in most regions. The pentose sugar in RNA is ribose and in DNA it is deoxyribose. Deoxyribse has one oxygen atom less on the 5â Carbon of the ribose sugar. Since RNA has few or no base pairs the Chargaff rule of equivalence of Adenine with Thymine and Cytosine with Guanine cannot be extended to DNA.