Imaging DNA in Solution with t

Introduc tion
DNA (deoxyribonucle ic acid) is a bio logical
polymer that st ores hereditary information
in almost all living organisms. Each strand
of DNA is a pat tern for duplicating new
strands of DNA, so, when cells divide,
each new cell gets an exact copy of
the DNA from the previous cell. DNA is
composed of two strands of repeating
units cal lednucleotides which are
entwined in the shape of a double helix.
Each DNA strand is 2.2 to 2.6 nanometres
wide. Individual DNA molecules can
cont ain hundreds of millions of nucleotides
and can be several mm long. Each
nucleotide is composed of a nucleobase,
a sugar residue and a phosphate group.
The nucleobases, adenine (A), cytosine
(C), guanine (G) or thymine (T), interact
(base pair) with a particular nucleobase
in an opposing strand of the double helix
by hydrogen bonding interactions; A
pai rswith T and C pairs with G. The sugar
residues are joined together by negatively
charged phosphate groups; which form
phosphodiester bonds between the 5’
and 3’ hydroxyl groups of each sugar
residue. The DNA double helix is stabilized
primarily by electronic interactions
between the nucleobases and Watson-
Crick base pairs (hydrogen bonds) between
the nucleobases in the opposing strands.