ugar, a phosphate group and a nitrogenous base.In Watson and Crick's model, the two strands of the DNA double helix are held together by hydrogen bonds between nitrogenous bases on opposite strands. Each pair of bases lies flat, forming a "rung" on the ladder of the DNA molecule. Base pairs aren't made up of just any combination of bases. A coding strand is a strand that contains the codons. On the contrary, the non-coding strand is the strand that contains the anti-codons. The coding strand is the strand of DNA that has the same sequence as the mRNA transcript.