SAMINAR REPORT ON SAMINAR REPORT ON DEOXYRIBONUCLEICDEOXYRIBONUCLEIC

ACIDACID

SUBMMITED BY

Shiwani sainiM.Sc I Year

Zoology

GUIDED BY Dr.B.L.Aggarwal Principal & HOD of Zoology Dr.ANUPMA GOUTAM

DEOXYRIBONUCLEICDEOXYRIBONUCLEICACIDACID

• INTRODUCTION:-• Deoxyribonucleic acid (DNA) is a nucleic acid that

contains the genetic instructions used in the development and functioning of all known living organism and some viruses. The main role of DNA molecule is the long-term

storage of information. HISTORY OF DNA RESEARCH:- First man who gave an idea about 3 dimensional structure of DNA was W.T Astbury .He studied with the help of X-ray crystallography & found that DNA is a steak of flat nucleotide.Maurice Wilkins continues Astbury's work and true x-ray diffraction he got the photography & found that DNA is 3

dimensional & nucleotides were arrange by the distance 3.4Å .• He suggest along with his co. worker’s is R.Franklin.• Later Watson & Crick studied photograph obtained by

Wilkins & contracted a modal for DNA & they published structure of DNA in 1953 in the general nature.

Rosalind Franklin Francis Crick James Watson

•Watson, Crick & Wilkinson got noble prize for double helical structure of DNA molecule.

STRUCTURE OF DNA:-STRUCTURE OF DNA:-

•The DNA polynucleotide chain has the form of a regular helix.•Helix has a diameter of about 20 Å helix marks one completes turn every 34 Å along its length.•Inter nucleotide distance in 3.4 Å.•The number of nucleotide in a turn is 10 Å.•Chains of two polynucleotide are antiperllal of each other.•Polynucleotide chain connected by hydrogen bonding.

Double helical structure of DNA

CHEMICAL NATURE OF DNACHEMICAL NATURE OF DNA :- :-• An organic molecule or polymorphic chemical compounds

made up of three elements:-• Phosphoric acid molecule called phosphate.• Pentose sugar called deoxyribose. • Nitrogen base called pyrimidines & purine.• These are 4 base found DNA.• Purine-, guanine (G),adenine(A)• Pyrimidine- thymine (T), cytosine(C).•Purine are heterocyclic compounds & 2 rigid pyrimidines are one ring.

CHEMICAL NATURE OF DNA

• DNA with these 3 elements called deoxyribose nucleotide (sugar+phosphate+nitrogen base = nucleotide) .

• Many nucleotide joined together forming polynucleotide.• Deoxyribose sugar+Nitrogen base =Nucleoside.

Nucleotide Nucleoside

TYPES OF DNA ( Alternative form of DNA TYPES OF DNA ( Alternative form of DNA double helix):-double helix):-

• There are three main alternative forms of DNA double helix found in the living system :-

• A-DNA• B-DNA• Z-DNA • A-DNA:- A-DNA is right handed DNA with 23Å helical

diameter.•It relative humidity a 75% with Na, K, Cs ions.•Base pair per turn 11•B-DNA:- Most commonly found DNA in the living plants & animal.•It is right handed DNA with 20Å helical diameter.•Base pair per turn 10.•E.g.-Mostly plants & animal have right handed DNA of B-form.

• Z-DNA:- Left handed DNA,18 Å helical diameter with 12 base pair per turn having very high salt concentration.

A-DNA,B-DNA,& Z-DNA

DNA AS A GENETIC MATERIAL:-DNA AS A GENETIC MATERIAL:- • DNA act as genetic material was a matter of discussions for a

long time in the past because chromosomes are made up of DNA ,RNA & Protein.

• Which part of the DNA responsible for heredity in chromosome had to be proved hence a number of experiments made by genetics & proved that only DNA is responsible for genetic information in the offspring

•Experiment given to prove DNA as genetic material:-

1.GRIFFITH’SEXPERIMENT ON BACTERIAL 1.GRIFFITH’SEXPERIMENT ON BACTERIAL TRANSFORMATION:-TRANSFORMATION:-

•Frederick Griffith in London in 1928 conducted the experiment in the lab on Diplococcus pneumonia & found that two strain of Diplococcus i.e. ‘S’ strain (virulent) & ‘R’ strain (nonvirulent) shown the transformation effect of DNA ‘S’ strain & ‘R’ strain.

• {‘s’strain=capsulated}• {’R’strain noncapsulated}

Transformation in Diplococcus phenomenon

2.BUT GRIFFITH FURTHER EXPERIMENTED SAME 2.BUT GRIFFITH FURTHER EXPERIMENTED SAME

EXPERIMENT ON THE MICE AS FOLLOWS:-EXPERIMENT ON THE MICE AS FOLLOWS:- • Live ’S’ + Mice→ Infected→ Mice dead

•Live ’R’ + Mice→ Infected→ Mice survived

• Heat killed ‘S’ + Live ’R’+ Mice→ Infected→ Mice dead

•Heat killed ‘S’ + Mice→ Infected→ Mice survived

•It prove that blood of dead mice showed the present of live‘s’ bacteria.•→Later Avery, Maccarty, Maclobed studied on the Griffith’s experiment by isolating heat killed ‘s’ cell in detailed & performed following information:-

1. Removed plysaconide capsule from heat killed ‘S’ cells + ‘R’ cells →Mice dead. 2.Remove protein frection from heat killed ‘S’ cells + ‘R’ cells →Mice dead. 3. Added DNAase in to heat killed ‘S’ cells + ‘R’ cells →Mice survived.

→Because third experiment disintegrated DNA & ‘R’ cells could not transform hence mice survived.

3. HERSHEY & CHAES EXPARIMENT ON 3. HERSHEY & CHAES EXPARIMENT ON BACTERIO PHASE TO PROVE DNA AS A BACTERIO PHASE TO PROVE DNA AS A GENETIC MATERIAL:-GENETIC MATERIAL:-

• →Hershey & chaes (1952) experimented on bacterial virus i.e. bacteriophase & found recombination between virus DNA & bacterial DNA as follows:-

• Both experiment Show on the transformed of DNA causing recombination has confirmed that DNA is the genetic material

CONCLUSION:-CONCLUSION:-