Nucleotides, Nucleic Acids,
and Genetic Information
This chapter introduces you to the structure and function of nucleotides and their polymers,
ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). The chapter begins with a discussion
of the various kinds of nucleotides and the large variety of their functions in cellular processes.
The nucleic acid polymers, RNA and DNA, are the primary players in the storage, transmission,
and decoding of the genetic material. Scientists use a variety of powerful techniques to
characterize and manipulate DNA from any organism. This chapter discusses the sequence-
specific cleavage of DNA by restriction endonucleases; DNA sequencing; amplification of DNA
by cloning in unicellular organisms such as bacteria and yeast; and the
DNA by the polymerase chain reaction.
Of the four major classes of biological molecules (amino acids, sugars, lipids, and
nucleotides), nucleotides are the most functionally diverse. They are involved in energy
transfer, catalysis, and signaling within and between cells, and are essential for the storage,
decoding, and transmission of genetic information.
Nucleotides are composed of a nitrogenous base linked to a ribose sugar to which at least
one phosphate group is attached. The eight common nucleotides, which are the monomeric
units of RNA and DNA, contain the bases adenine, guanine, cytosine, thymine, and uracil.
The best known nucleotide is the energy transmitter adenosine triphosphate (ATP), which
is synthesized from adenosine diphosphate (ADP). Transfer of one or two of the
phosphoryl groups of ATP is an exergonic process whose free energy can be used to drive
an otherwise nonspontaneous process.
Introduction to Nucleic Acid Structure
Nucleic acids are polymers of nucleotides in which phosphate groups link the 3
positions of neighboring ribose residues. This linkage is called a phosphodiester bond
because the phosphate is esterified to the two ribose groups. The phosphates are acidic at
biological pH and so the polynucleotide is a polyanion.