Hello everyone, I am Dr. Ujwalkumar Trivedi, Head of Biotechnology Department at Marwadi University Rajkot. I teach Molecular Biology to the students of M.Sc. Microbiology and Biotechnology. The current presentation tries to address essential questions of RNA world and as to how and why DNA evolved as genetic material.

1. Advance Course on
“Nucleic Acid Chemistry”
April 02, 2020
Course-2, Quarantine Classes:
An Initiative to provide free online education to Life Science students
across India.
Essential Questions in Nucleic Acid Chemistry
Dr. Ujwalkumar Trivedi, Ph.D., FICS
Head
Department of Biotechnology
Marwadi University Rajkot

2. 2
1. Why DNA replaced RNA in evolution?
2. Why Thymine replaced Uracil in DNA?
3. Why Nucleic Acids are Never Synthesized in
3’ to 5’ direction?
4. Why Nucleic Acids contains only Pentose
Sugars (Ribose) and Not Other Sugars.
5. Why DNA double helix is Anti-Parallel?
Outline

3. Structure of nucleotides

4. Structure of N-Bases

5. Major purine bases of nucleic acids

6. Major pyrimidine bases of nucleic acids

8. Deoxyribonucleotides of nucleic acids

9. Ribonucleotides of nucleic acids

10. Phosphodiester linkages in the covalent
backbone of DNA and RNA

12. Why DNA replaced RNA in
evolution?

13. RNA has a short half life due to its 2’OH
which is absent in DNA.

14. Why Thymine replaced Uracil in
DNA?

15. Some well-characterized nonenzymatic
reactions of nucleotides

16. If Uracil would have been an integral part of DNA, then in the above case, the
next cycle of replication would have incorporated Adenine instead of Guanine
in the newly synthesized strand which will lead to mutation. Also our repair
system would have had great difficulties in detecting this mutation. The
methyl group on thymine is like a tag since cytosine deamination will not
generate thymine.

19. Why Nucleic Acids are Never
Synthesized in 3’ to 5’ direction?

22. Strand Abortion

23. Why Nucleic Acids contains only
Pentose Sugars (Ribose) and Not
Other Sugars?

24. Deoxyribonucleotides of nucleic acids

25. Ribonucleotides of nucleic acids

26. Why not Triose or Tetrose in Nucleic Acids?

27. Why Not Hexose Sugar in Nucleic Acids

28. Why only Beta Ribose in Nucleic Acids?

29. Why DNA double helix is Anti-
Parallel?

30. 12 Angstrom width
8.5 Angstrom depth
6 Angstrom width
7.5 Angstrom depth

31. Hydrogen-bonding patterns in the base pairs
defined by Watson and Crick

32. Chemically made parallel DNA will assume Hoogsteen Base Pairing

33. Such kind of improper stacking makes the parallel DNA
thermodynamically less stable and hence is not favored.

34. Thank You
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Website: https://www.marwadieducation.edu.in/