Introduction to Nucleic acids

1. Nucleic Acids
Dr. Karthikeyan Pethusamy

2. Nucleic acids are polynucleotides
• Polysaccharides
• Polypeptides
• Polynucleotides

4. Sugar: Ribose, Deoxy ribose, Dideoxy ribose
Dideoxy ribose

5. Ribose  Deoxyribose
FAD
Hydroxy
urea

6. What exactly is happening?

7. Base: Purine, Pyrimidines

8. Sources of purine ring atoms

9. Purine Bases
Adenine Guanine
Hypoxanthine Xanthine
Uric acid

11. Deamination of ‘methylated cytosine’ will produce
a) Uracil
b) Thymine
c) Hypoxanthine
d) Adenine

12. Why CpG dinucleotides are rare in vertebrate
genomes?

13. Pyrimidine Bases

14. Nucleosides

15. Nucleotide Monophosphate (NMP)

16. Cyclic Nucleotide Monophosphate (NMP)

17. Nucleotide diphosphate (NDP)

18. Nucleotide triphosphate

21. Polynucleotide

22. At physiologic pH, DNA is
a. Positively charged
b. Negatively charged
c. Amphoteric
d. Uncharged

23. DNA electrophoresis

24. Chargaff’s rule
In a double stranded DNA,
•Number of Purines = Number of pyrimidine
•[A+G] = [T+C]
[A] = [T]
[G] = [C]
[A+T] # [G+C]
Note: Chargaff’s rule is NOT applicable for RNA and ssDNA.

25. Bacteria X has an adenine content of 33% in its genome. What is the
expected thymine content in the genome of X?
a. 22%
b. 33%
c. 44%
d. 67%

26. In a sample of DNA, if adenine content is 23%,
what will be the amount of guanine?
a. 23%
b. 46%
c. 54%
d. 27%

27. Why purine pairs with only pyrimidine?
Why purine-purine & pyrimidine-pyrimidine base pairing is not
possible?

30. DNA vs RNA

31. Which of the following bond is responsible for
holding two strands of DNA together?
a) N-Glycosidic bond
b) Van der Waals interaction
c) Salt bridges
d) Hydrogen bond

32. Secondary structures of RNA

33. tRNA – secondary structure

34. Double stranded RNA exists in
a) A - DNA like conformation
b) B - DNA like conformation
c) Z - DNA like conformation
d) None

35. Which of the following is the substrate for the
enzyme ribonucleotide reductase?
a) Nucleoside monophosphate
b) Nucleoside diphosphate
c) Nucleoside triphosphate
d) All of the above

36. Triplex DNA is formed because of
a) Palindromic sequences
b) Guanosine repeats
c) Polypyrimidine sequences
d) Hoogsteen pairing

37. Nitrogenous bases absorb UV-light
lmax ~ 260 nm

38. DNA estimation can be done by
a. Colorimeter
b. Spectrophotometer
c. pH meter
d. Luminometer

39. Hyperchromicity of Denaturation

40. 260/280 ratio

41. Classes of RNA

42. Ame’s test for mutagenicity
Suspected
Mutagen
Liver extract