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In the centre
of every plant
cell - from
algae to sunflowers
- and
in the centre
of every
animal cell
- from snails
to you and
me - there’s
a copy of the
organism’s
genetic
material.
The DNA carries a complete
blueprint of the
organism. It’s what transfers
characteristics from one generation
to the next.
At the chemical level the
cells of all plants and all
animals contain DNA in the
same shape - the famous
"double helix" that looks
like a twisted ladder. What’s
more, all DNA
molecules
- in both
plants
and animals
- are made from the same
four chemical building blocks
- called nucleotides. What
is different is how these
four nucleotides in DNA are
arranged.
 Click on the image to view a bigger version Genetics
Genetics is about
storing and passing on
messages.
These genetic messages are
stored in your DNA, which
is inside almost every cell
in your body. DNA tells
cells what they’re supposed
to do, when,
where and how
- to keep
your body
working well.
Our understanding
of genetics
stems from the discovery
of the DNA molecule
in every cell, which carries
the genetic information.
What is DNA?
DNA is an acid that carries
(as genes) all the information
which we inherit from
our parents. It controls everything
about the way you
look, from the colour of your
eyes to how tall you are to
the width of your feet. Your
DNA is like your thumbprint.
It is yours and yours alone.
Unless you have an identical
twin, no one else on the
planet has exactly the same
DNA as you.
James Watson and
Francis Crick found out
that DNA looks like two
threads twisted around
each other, held together
by many bridges between
the strands. It almost looks
like a spiral staircase. This
shape is called a double
helix. The genetic information
is stored on the threads.
Where can DNA be
found?
In the nucleus of almost
every cell in your body,
and that of every other living
thing, is the collection
of DNA needed to make
you. DNA in the nucleus
is grouped into 23 sets of
chromosomes that are called
your "genome". In each
chromosome, the DNA is
grouped into "genes". Your
genome contains about
35,000 genes. Each gene
carries information that tells
the cell to make a unique
protein that will perform a
special function.
How does something as small as DNA molecules contain
all of the instructions to make your whole body and keep it working? Just as a large number of words can be made from only a few letters,
so DNA can make lots of different instructions from a few building blocks.
How knowledge about DNA affects us
Scientists are working to understand the genetic messages
that make some people respond to medicines differently
than others and make some people more prone to certain diseases than others. They use this knowledge to make new medicines to help people live healthier lives.
DST launched a three-year programme to tell South Africans about Biotechnology (see www.pub.ac.za). This is the part of science that uses the DNA building blocks of life to make useful products from living things.
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