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WHAT
IS DNA?
DNA is often referred to as the “building block of
life”. This is because it stores, in coded form, all
of the genetic information needed to create a living being.
Discovering the structure of this amazing molecule was one
of the most important scientific breakthroughs of the 20th
century. The first description of DNA structure was published
in 1953 by James Watson and Francis Crick. Their research
would earn them the 1962 Nobel Prize in Medicine and Physiology.
The
structure of DNA
Each molecule of DNA consists of two strands, which can
be pictured as the long uprights of a ladder. Along the
length of each strand are “bases”, and bases on
one strand join to bases on the other like the ladder’s
rungs. This ladder is twisted into the shape of a winding
staircase, giving the molecule its now-famous “double
helix” description.
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The language of DNA
There are just four types of base: A (adenine), T (thymine),
C (cystosine) and G (guanine); and they join to each other
according to strict rules. An A on one strand always pairs
with a T on the other, and a C always pairs with a G.
It is these four letters (A, T, C and G) that form the simple
coding language used by DNA. Although there are only four
letters, they can be combined in a huge variety of sequences,
which means that DNA can store an enormous amount of information.
This information provides instructions for cells. Various
combinations of three of the four letters code for the production
of twenty different amino acids. These amino acids are then
combined in different sequences to build various types of
protein molecules, and it is these proteins that are responsible
for the way that a living body is built and functions.
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