INTRODUCTION
Informational macromolecules are those through which genetic in
formation actually flows. Genetic information may be defined as that
primarily required to assemble a protein needed to perpetuate biological
order, but the definition applies also to the information for ribonucleic
acids (RNAs) which are not translated into protein. Deoxyribonucleic
acids (DNA) functions as the repository for information or coding se
quences ultimately destined to appear either in RNA or protein, and in
noncoding sequences which can act as signals for such things as initiation
and termination of the biosynthesis of a RNA chain. Within the cell the
informational sequences are transmitted on which specific proteins are
synthesized.
The DNA dependent RNA polymerases (E. C. 2.7.7.6.) are the key
enzymes implicated in the first step of genetic information flow from DNA
to protein. The term DNA dependent RNA polymerases is used to designate
enzymic activities which, using DNA templates, catalyze the sequential
assembly of the four ribonucleoside triphosphates into RNA molecules.
The synthetic reaction requires the presence of a DNA or a polydeosy-
ribonucleotide template and a divalent metal ion. The main features of
the transcription reaction consist of the enzyme locating and binding to
specific sites on the DNA, initiating a RNA chain de novo, extending the
chain by moving along the DNA using only one strand as a template to
direct the polymerization of the four ribonucleoside triphosphates into
1