Nucleic Acids are two types-DNA and RNA. DNA is described here which is genetic material. Its biochemical and physical structures are described. There are different types of DNA which are also described.

1. Nucleic acids
Md Ekramuddin

2. Discovery
• Friedrich Miescher isolated the DNA in 1869.
• He named this as ‘nuclein’ for finding from
nucleus
• From pus cells(white blood cells)
• In 1889 Richard Altmann creates the term
nucleic acid
• In 1953 Watson and Crick determined the
structure of DNA.

3. Types
• Two types
A) DNA(Deoxy ribonucleic acid)
B) RNA( Ribonucleic acid)

4. Building block
• Both DNA and RNA are polymer of nucleotides
• They are building blocks(monomer)
• Each nucleotide is formed by three
components
1. Phosphate
2. Pentose sugar
3. Nitrogenous bases

5. Phosphate and sugar
• Single,two or three phosphates present
• Sugar is pentose. Ribose sugar in RNA and De-
oxy ribose sugar in DNA
• One oxygen atom absent in 2’C of deoxyribose
sugar
• Phosphate links with sugar by ester bond
• They form the back-bone of nucleic acid
polymer

6. Sugars in Nucleic Acids

7. Nucleotide
In RNA
In DNA

8. Nitrogenous Bases
• C-N rings
• Two types- purines and pyrimidines
• Purines-Adenine(A) and Guanine(G)
• Pyrimidines- Thymine(T), Cytosine (C) and
Uracil(U)
• Four types of bases found-A,T,G,C in DNA and
A,U,G,C in RNA
• They are also two kinds- amino base(A,C) and
keto base(C,G,U)

9. Two kinds of C-N rings

10. Purines
Adenine Guanine

12. Pyrimidines

14. Organisation of nucleotide(eg.AMP)

15. Polynucleotide Strand

16. Complemetarity[ A=T]

17. Complemetarity[ CG]

18. Double strand formation in DNA

19. Watson Crick Model
• Watson and Crick demonstrated a model in 1953
which explain all the physical and chemical
features of the DNA
• Maurice Wilkins and Rosalind Franklin helped
them with their data analysis
• Won the Noble Price in Physiology and Medicine
at 1962 which they shared with Maurice Wilkins
but not with the Rosalind Franklin due to her
unfortunate death in 1958 at the age of 37

20. Features of the model
• Double helical, antiparallel
structure
• Right handed B-DNA
• Sugar and phosphate form
the backbone, nitrogenous
bases packed inside in stacks
• Diameter 20A
• Length of helix 34A
• Major and minor grooves
• Complementary base
pairing[A=T; CG]
• Total purine=total pyrimidine
• 10 pairs nucleotide in each
turn

21. Different kinds of DNA
• Right handed and left handed- right is regular
• B-DNA is regular, other forms are occassional
• Other forms are A and Z DNA
• Some very rare conformation- C,D and E-DNA
• Super-coiled state (described by Vinograd)
• Tertiary or triple stranded or H-DNA (formed
by unusual Hoogsteen base pairing, T=AT and
CGC)

22. A,B and Z-DNA

24. Hoogsteen base pairing

26. Hyper and hypochromicity
• DNA can absorb medium length UV
light(~280nm)
• Denatured DNA can absorb more light called
hyperchromicity
• Compact or supercoiled DNA absorbs less light
called hypochromicity

27. Thank you