DEOXYRIBONUCLEIC ACID

SAMINAR REPORT ON DEOXYRIBONUCLEICACID : 

SAMINAR REPORT ON DEOXYRIBONUCLEICACID SUBMMITED BY Shiwani saini M.Sc I Year Zoology GUIDED BY Dr.B.L.Aggarwal Principal & HOD of Zoology Dr.ANUPMA GOUTAM

DEOXYRIBONUCLEICACID : 

DEOXYRIBONUCLEICACID 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

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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

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

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Double helical structure of DNA

CHEMICAL NATURE OF DNA :- : 

CHEMICAL 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.

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CHEMICAL NATURE OF DNA

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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 double helix):- : 

TYPES OF DNA ( Alternative form of DNA 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.

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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 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.

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{‘s’strain=capsulated} {’R’strain noncapsulated} Transformation in Diplococcus phenomenon

2.BUT GRIFFITH FURTHER EXPERIMENTED SAME EXPERIMENT ON THE MICE AS FOLLOWS:- : 

2.BUT GRIFFITH FURTHER EXPERIMENTED SAME EXPERIMENT ON THE MICE AS FOLLOWS:- Live ’S’ + Mice→ Infected→ Mice dead Live ’R’ + Mice→ Infected→ Mice survived

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

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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 BACTERIO PHASE TO PROVE DNA AS A GENETIC MATERIAL:- : 

3. HERSHEY & CHAES EXPARIMENT ON BACTERIO PHASE TO PROVE DNA AS A GENETIC MATERIAL:- →Hershey & chaes (1952) experimented on bacterial virus i.e. bacteriophase & found recombination between virus DNA & bacterial DNA as follows:-

CONCLUSION:- : 

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