That's easy! Each sugar unit in DNA and RNA bind to form one of four nucleotide bases. Both the DNA and the RNA use the bases A,C and GB. While DNA uses T, RNA uses U. The sequence of bases along the strands of DNA and RNA is the genetic code that tells the cell how to make proteins. In DNA, the bases of each strand bind to the bases on the other strand, forming the double-helix structure. In DNA, A’s can only bind to T’s and C’s can only bind to G’s. The structure of a DNA helix is preserved in a protein-RNA cocoon called a chromosome.