A DNA chain serves as a
template in (DNA
duplication) as well as in
(RNA formation). In both processes the
pairing of the two polynucleotide chains
of the original DNA is broken
by the breaking of hydrogen bonds for
the chains to be exposed as templates.
The reaction is ed by specific
enzymes in transcription and in
.

In the enzyme DNA
polymerase catalyzes the formation of a
new polynucleotide chain using free
in solution and putting them
in the new chain according to the DNA
template exposed and to the rule A-T,
C-G.

In the enzyme RNA
polymerase makes a new polynucletide
chain according to the DNA template
exposed obeying, however, the rule AU, C-G.

In replication the original template DNA
chain is kept bound by hydrogen bonds
to the newly formed DNA chain and a
new DNA molecule is then created. In
the association between
the template DNA chain and the newly
formed RNA is undone and RNA
constituted of only one
chain is liberated.