DNA
history
structure
X-Ray diffraction image of DNA
base pairing principle
base pairs
bonding patterns of DNA
base stacking different conformations of DNA
different forms of DNA
function of DNA
replication
encoding information
mutation/recombination
gene expression
Application of DNA
2. DNA
DNA or deoxyribonucleic acid is a genetic
material that transfer the genetic information
from one organism to their off spring.
Located in nucleus and mitochondria
The information in DNA is stored as code
(made up of A,G,C,T).
99% of base are same . The order of bases
determines the individuality.
3. HISTORY
1866-Gregor Mendel finds how parents pass
on discrete inheritance traits
1928-Fredrick Griffith proved that bacteria
could change their character by transformation
1949-Edwin Chargaff discovers that in DNA
molecule A=T and G=C
4. 1952-Alfred Hershey & Martha Chase
confirmed that DNA is a genetic material
1952-Maurice Wilkins & Rosalind Franklin
found that DNA was at least a double helical
shape.
1953-Games Watson & Francis Crick found
that DNA is made up of 2 polynucleotide
5. STRUCTURE
DNA is a long chain polymer of
nucleotides
Consist of:
Deoxyribose=5 pentose sugar
Phosphate group
Organic bases
Adenine ,Guanine (purines)
Cytosine ,thymine (pyrimidines)
DNA is a double helix with 2
strands which gives ladder like
shape with base pairs
6. X-ray diffraction image of DNA
Total length of DNA in
human genome is 1.8 meters
Rosalind Franklin used X-
ray diffraction to understand
the physical structure of
DNA
X-rays are diffracted
resulting in over lapping
circles
Diffracted waves interferes
one another
7. BASE PAIRING PRINCIPLE
Base pairing is an application of hydrogen
bonding principle
Adenine= Thymine pair interacts through
2 hydrogen bonds
Guanine= Cytosine pair interacts through
3 hydrogen bonds
The diameter of the double helix is 20
Angstroms
8.
9. BONDING PATTERNS OF DNA
The nitrogenous base are single or double ring
structure that are attached to the 1st carbon atom
The base is attached to the sugar by N-glycosidic
bond
Nucleoside is converted into nucleotide by
attachment of a phosphate group.
The linkage between the nucleotides in a
polynucleotide is a phosphodiester bond
The 5’ carbon atoms has not participated in
phosphodiester bond and called 5’ end
The molecule which are un reacted called as 3’
hydroxyl group or 3’ end
10. Hydrogen bonds gives stability
It occurs between neucleobases& is internal
to DNA
HB also influence on replication
BASE STACKING:
It is a non-covalent interaction
Depend on vanderwaal’s dispersive forces
Electrostatic effects influence stability
Purines stacks strongly than pyrimidines
It influence replication
11. DIFFERENT CONFORMATION OF DNA
FEATURE B DNA A DNA Z DNA
TYPE OF HELIX RIGHT-HANDED RIGHT-HANDED LEFT-HANDED
NO.OF. BP PER
TURN
10 10 12
DISTANCE
BETWEEN BP(nm)
0.34 0.29 0.37
DISTANCE
COMPLETE PER
TURN(nm)
3.4 3.2 4.5
DIAMETER(nm) 2.37 2.55 1.84
MAJOR GROOVE WIDE,DEEP NARROW,DEEP FLAT
MINOR GROOVE NARROW,SHALLO
W
WIDE,SHALLOW NARROW,DEEP
13. FUNCTION OF DNA
REPLICATION
ENCODING INFORMATION
MUTATION/RECOMBINATION
GENE EXPRESSION
14. REPLICATION
Double helix unwinds and act as a template and forms
double helix with the aid of DNA polymerase
ENCODING INFORMATION
A codon specifies a particular amino acid that which
produce a particular protein
MUTATION/RECOMBINATION
DNA plays a role in evolution of a species
DNA can repair itself through recombination and mutation
occurs due to illegal base pairing
Both mutation and recombination either beneficial or create
genetic diseases
15. GENE EXPRESSION
Cells from different tissues & organ, look & behave
differently
DNA can respond to produce a particular protein by
express a particular protein through transcription and
translation
Transcription-making RNA
Translation-making protein
16. APPLICATION OF DNA
DNA FINGER PRINTING
DNA SEGUENCING
DNA VACCINES
RECOMBINANT TECHNOLOGY