The World of DNA
DNA stands for deoxyribonucleic acid. It consists of
two associated polynucleotide strands forming a double
The helix makes a complete turn avery
3.4 nm and there are about 10.5 basepairs per turn.
On the outside of the double helix the spaces between
the intertwined strands form two helical grooves of
different widths described as the major groove and the
The sequential arrangement of base pairs in a DNA molecule
can be sensed via the major groove and the minor groove
as a surface pattern of hydrogen donors, hydrogen acceptors
and hydrophobic patches.
DNA-binding proteins that form
DNA sequence specific complexes usually recognize their
cognate DNA segment via a DNA-binding domain which has
a surface pattern complementory to the pattern of the
major and/or minor groove of that particular DNA segment.
DNA contains a coded representation of all the proteins
in the cell. Other molecules such as sugars and fats are synthesised
by proteins (enzymes) so their structures are indirectly
coded by DNA.
DNA also contains all the information
required to make the correct amount of protein at the
correct time, thus controlling all biological processes
from those of day to day life such as metabolic activity
to those of embryogenesis and fetal development.
The human genome contains 3x109 base pairs of DNA divided
into 23 chromosomes which if linked together would form
a thread of 1 meter with a diameter of 2 nm. This DNA
codes for about 105 different proteins.
In fact only
about 2-4 % of the total coding capacity in the human
DNA is used for coding of different genes, the rest
of it probably has other more structural and organizational