Dna

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.

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

 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

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

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

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

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

 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

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

FUNCTION OF DNA
 REPLICATION
 ENCODING INFORMATION
 MUTATION/RECOMBINATION
 GENE EXPRESSION

 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

 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

 APPLICATION OF DNA
 DNA FINGER PRINTING
 DNA SEGUENCING
 DNA VACCINES
 RECOMBINANT TECHNOLOGY

Dna

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Dna