Which of these is a difference between a dna and an rna molecule? which of these is a difference between a dna and an rna molecule? dna contains nitrogenous bases, whereas rna contains phosphate groups. dna is a polymer composed of nucleotides, whereas rna is a polymer composed of nucleic acids. dna contains five-carbon sugars, whereas rna contains six-carbon sugars. dna is usually double-stranded, whereas rna is usually single-stranded. dna contains uracil, whereas rna contains thymine?