Three Parts, One Rung, Every Instruction

You'll learnhow three parts make a nucleotide, how nucleotides form a backbone, and how bases pair.

A nucleotide is three pieces of chemistry — a phosphate, a five-carbon sugar and a nitrogenous base — and the molecule holding every instruction for building you is nothing more than those three, linked over and over in one direction. Only the base ever changes, so the message can only be there. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · PHOSPHATE + SUGAR + BASE · BACKBONE = COVALENT · RUNGS = HYDROGEN BONDS · ANTIPARALLEL 5′→3′ · v6

three parts · one covalent backbone · rungs that let go

Before you start

What you're looking at

One nucleotide assembling from a phosphate, a five-carbon sugar and a base. A solid stick is a covalent bond; a dashed line is a hydrogen bond.

The question

If the sugar and phosphate never change along a strand, where is the information stored?

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