DNA : Double Helix formation

1
DNA Double Helix formation
Simple Diagrams of DNA structure
A right-handed double-helical conformation of
DNA normally seen in solution described by James
Watson and Francis Crick (1953). A second DNA
conformation (A form) is seen in unhydrated DNA
(fibres or crystals of oligonucleotides). B-DNA
also differs from other DNAs (i.e., A, C, D, E,
and Z) by having 10 base pairs per turn, 36
rotation per base pair, 3.4A vertical rise per
base pair and 23.7A helical diameter.
Double Heilx structure
AT/GC paring
Protein Folding and Engineering Lab
2
DNA Denaturation and Renaturation Hybridization
DNA-DNA hybridization When DNA is heated to
denaturation temperatures to form single strands
and then cooled double helices will re-form
(renaturation) at regions of sequence
complementarity. This technique is useful for
determining sequence similarity among DNAs of
different origin and the amount of sequence
repetition within one DNA.
Protein Folding and Engineering Lab
3
DNA Chip Foundation
1st report Fodor, S.P.A.et al. Nature 1993,
364, 555-556 (Affimatrix, http//www.affimatrix.co
m)
DNA Chip a high density array of short DNA
molecules bound to a solid surface for use in
probing a biological sample to determine gene
expression, marker pattern or nucleotide sequence
of DNA/RNA.
Protein Folding and Engineering Lab
4
DNA Chip and Now
ArrayItTM substrate (http//arrayit.com)
schematic illustration of glass slide
surface.  positively charged reactive amino
groups on a polished, atomically flat glass
substrate. 
Protein Folding and Engineering Lab
5
Usage of DNA Chips

• Main target of DNA Chips
• Diagnostics
• Biological research

Protein Folding and Engineering Lab