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Base
Analogues -
A chemical substance resembling a base is called a base analogue. A base analogue may be incorporated into newly synthesized DNA instead of a normal base.
The
pyrimidine
analogue
5-bromouracil
(5-BU)
is
structurally
very
much
similar
to
thymine.
If
bacteriophages
are
grown
in
the
presence
of
5-BU
they
incorporate
the
substance
as
if
it
were
thymine.
5-BU
does
not
have
a
lethal
action
because
it
is
incorporated
in
place
of
T
and
functions
almost
normally.
5-BU
can,
however,
undergo
internal
rearrangement
(tautomerization)
from
the
usual
keto
state
to
the
rare
enol
state.
5-BU
now
pairs
with
guanine
instead
of
adenine,
the
natural
partner
of
thymine.
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