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DNA is an ideal molecule to
transfer genetic messages to
every cell of your body.
When an egg and sperm met to
form the first cell that was
to become you, you were
given the complete genetic
code that all of your cells
will use for the rest of
your life.
In that first cell, half
of the chromosomes (half of
the DNA molecules) came from
your father and the other
half came from your mother.
The first cell divided to
become two cells, these both
divided to become four, then
eight then 16 and so on.
Some of the cells in your
body are still dividing, for
example to produce new skin
or blood cells. Most of the
time a cell divides
perfectly and each of the
DNA molecules is copied
exactly, with one copy going
to each of the new cells. If
mistakes are made, they are
fixed or the cell is marked
for destruction.
If a problem occurs in
this process the new cells
often die, but on rare
occasions the faulty cells
survive and can cause a wide
range of problems. However,
sometimes these faults
(mutations) can be
beneficial for the organism:
this is the basis for
evolution.
In order to make a copy
of itself, the DNA molecule
unzips lengthwise, leaving
unpaired bases along each
backbone. Nucleotides, which
are made up of a sugar, a
phosphate and one of the
four bases, float freely in
the nucleus. Because A can
only pair with T and G can
only pair with C, the
nucleotides match up with
the unpaired bases along the
DNA backbone. Like building
blocks, they form a new
strand that is complementary
to (matching) the sequence.
This forms strands identical
to the original strand
before it unzipped.
Several teams of
scientists are trying to
make a new form of living
being from non-living
chemicals. They will need to
find this new 'Los Alamos
Bug' the equivalent of a
cell wall and make sure it
can metabolise and reproduce
itself. The Bug will use a
completely different way to
hold genetic instructions
than DNA. Currently,
scientists are looking to
use a molecule called
peptide nucleic acid (PNA).
Like DNA, PNA is made up of
two strands containing the
nucleotides A, T, G and C
which complement each other,
but the molecule itself is
soluble in fat instead of
water. |
