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Surprisingly, while the DNA
molecule is very long, it is
stunningly simple. DNA looks
like an incredibly long
twisted ladder. This shape
is called a double helix.
The sides of the ladder
are a linked chain of
alternating sugar and
phosphate molecules. The
rungs connect to the sugar
molecules and are known as
bases.
There are four bases -
adenine (A), thymine (T),
guanine (G) and cytosine
(C). Each rung is made up of
two bases that link
together. Because of their
chemical nature, A will only
link with T and G will only
link with C.
DNA from all living
organisms is made of the
same sugar and phosphate
molecules and the same four
bases. Whether DNA is in
your cells, those of a
cactus, of a worm or a
bacterium, it is made of the
same chemicals and has the
same structure.
The only difference is
the order or the sequence of
the bases in the DNA
molecule. It is this
sequence that is referred to
as the genetic code, and why
it is sometimes called the
code of life.
Try some DNA line dancing -
work sheet [PDF 144kb | 2
pages ] |
