Genetic Code
Genetic
information
specifies
the
correct
sequence
of
the
amino
acids
in
a
polypeptide
chain.
Each
of
the
twenty
different
types
of
amino
acids
is
represented
in
a
DNA
molecule
by
a
triplet
code,
consisting
of
sequences
of
three
nucleotides.
That
is,
the
sequence
C,
G,
T
in
a
DNA
strand
represents
one
kind
of
amino
acid;
the
sequence
G,
C,
A
represents
another
kink;
and
T,
T,
A,
still
another
kind.
Other
sequences
encode
instructions
for
beginning
or
ending
the
synthesis
of
a
protein
molecule.
The sequence of nucleotides in a DNA molecule dictates the sequence of amino acids of a particular protein molecule and indicates how to start or stop the protein's synthesis. This method of storing information for protein synthesis is the genetic code. However, because DNA molecules are located in the nucleus and protein synthesis occurs in the cytoplasm, and because the cell must keep a permanent copy of the genetic instructions, the genetic information must somehow get from the nucleus into the cytoplasm for the cell to use it. RNA molecules accomplish this transfer of information.
| The genetic code is said to be universal because all species on earth use the same DNA base triplets to specify the same amino acids. Researchers deciphered the code int eh 1960s. When the media mentions an individual's genetic code or that scientists are currently breaking the code, what they really are referring to is the sequence of DNA bases comprising a certain gene or genome-not the genetic code (the correspondence between DNA triplet and amino acid). |
