Molecular biology and genetics for undergraduate medical students

1. Dr. Farhana Atia
Assistant Professor
Department of Biochemistry
Nilphamari Medical College, Nilphamari
Email: farhana.atia@gmail.com
FUNDAMENTALS OF MOLECULAR BIOLOGY
AND GENETICS

2. NUCLEIC ACID
 DNA
 RNA
 NA are polymer of nucleotide covalently linked
with one another.
 Nucleotide: Building blocks of NA consisting
 Nitrogenous base
 Pentose sugar
 Phosphate group
 Nucleoside: Derivatives of purine & pyrimidine
that have a sugar linked to a ring nitrogen.
(base+ sugar).

3. NITROGENOUS BASE
Nitrogenous base
Purine: adenine, guanine
Pyrimidine: cytosine, uracil, thymine
Unusual base
 Heterogenous ring
 Numbered as
 1-6 in pyrimidine
 1-9 in purine

5. SUGAR
 Sugar
Deoxyribose
Ribose
 Ring
 C are numbered as
1′- 5′ (prime)
 Structure

6. PURINE
 9 MEMBERED RING
 Arranged in anti-clockwise
 Adenine : 6 amino purine
 Guanine : 2 amino 6 oxopurine
 Unusual base (during metabolism of
purine)
Hypoxanthine : 6 oxopurine
Xanthine : 2, 6 dioxopurine
Uric acid : 3 oxopurine

7. Adenine Guanine

8.  Pharmacologically
Methylated purine of plants have
pharmacological properties
 Methylated xanthine derivative of caffeine of
coffee (1, 3, 7 trimethyl xanthine)
 Theophylline of tea ( 1, 3 dimethyl xanthine)
 Theobromine of coca ( 3, 7 dimethyl xanthine)

9. PYRIMIDINE
 6 membered ring
 Arranged in clockwise direction
 Cytosine : 2 oxo 4 amino pyrimidine
 Uracil : 2, 4 dioxo pyrimidine
 Thymine : 2, 4 dioxo 5 methyl pyrimidine (only
base that have methyl group)
 Methylation : 5 methyl cytosine
 Hydroxy methylation : 5 hydroxy methyl
cytosine
 Glycosylation & acetylation : 4 acetyl cytosine

10.  Uracil : 2, 4 dioxo pyrimidine
 Thymine : 2, 4 dioxo 5 methyl pyrimidine
 Cytosine : 2 oxo 4 amino pyrimidine

11. Base Nucleoside Nucleotide
Adenine Adenosine
AMP
ADP
ATP
Guanine Guanosine
GMP
GDP
GTP
Cytosine Cytidine CMP
Uracil Uridine UMP
Thymine Thymidine TMP

12. Position of attachment
 Nucleoside consists of purine/ pyrimidine & a
cyclized sugar.
 Most of a D-ribose or 2′ deoxyribose linked
via a covalent β N glycosidic bond to N9 of
purine & N1 of pyrimidine.
 Numbering of a sugar atom employ a prime,
distinguished sugar from those of heterocyclic
base.

13. Nucleoside

14. NUCLEOTIDE
 Mono, di or tri phosphate ester of nucleoside.
 First PO₄ group is attached by an ester
linkage to the 5′ hydroxyl group of pentose.
 DNA- 5′ deoxyribonucleotide
 RNA- 5′ ribonucleotide
 2nd & 3rd PO₄ groups are attached by high
energy phosphate bond.
 PO₄ groups are responsible for negative
charge of Ntide & Nside.

16. FUNCTIONS OF N’TIDE
 Essential for all living cells. DNA & RNA can
not be synthesized without nucleotide.
 N’tide has group transfer potential or
participate in energy transfer (ie. Energy
currency of cell).
 Serve as a carrier of activated intermediates in
the synthesis of some carbohydrate, lipid &
protein, Eg. UDP-glucose, UDP-galactose.
 Act as a physiological mediator. Eg. C-AMP, c-
GMP, ADP in platelet agregation.

17.  As a 2nd messenger participate in diverse
regulatory functions of cells.
 Inhibit or activate key enzymes- c-AMP
dependent protein kinase
 ADP level regulates the rate of mitochondrial
phosphorylation.
 Structural component of coenzymes- NAD,
NADP, FAD, FMN.
 Allosteric modifier of some enzymes- ATP,
CTP

18.  Act as a carrier of active molecule in anabolic
process (CHO, prot, lipid)
 Synthetic N’tide analog are used as
chemotherapy- Allopurinol treat hyperuricemia &
gout.
 Non hydrolyzable analog of N’tide provide
research tool.
 Hazardous effect: N’tide absorb UVL. UVL is a
potent mutagen.

19. Nucleic acids are polynucleotide