Termination codons do not code for any amino acids and hence cause
termination and release of polypeptide chains.
Apparently no tRNA species has anticodons complementary to the termination codons.
There are mRNAs with single termination codons and also mRNAs with two successive termination codons (e.g. MS2 coat protein mRNA).
Termination
codons
are
not
read
by
any
tRNA
molecules
but
by
proteins
called
release
factors.
In
prokaryotes
there
are
three
release
factors
RF-1,
RF-2
and
RF-3.
RF-1
recognizes
UAA
and
UAG,
while
RF-2
recognizes
UAA
and
VGA.
RF-3
stimulates
RF-1
and
RF-2.
In
eukaryotes
a
single
release
factor
(RF)
recognizes
all
three
termination
codons.
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