LECTURE I NUCLEOTIDES CHEMISTRY AND SIGNIFICANCE

1. LECTURE I
NUCLEOTIDES CHEMISTRY AND SIGNIFICANCE

2. LEARNING OBJECTIVES
• Nucleic acids and Nucleotides
• Structure of Nucleotide
• Types of Nucleotides
• Functions of Nucleotides
• Pathological conditions associated with disruption in nucleotide
metabolism

3. NUCLEIC ACIDS
Nucleic acids are basically biopolymers which are made up of
monomeric units called Nucleotides.
OR
Nucleotide is a building block of nucleic acid.
Nucleic acid holds the genetic information. The fact that different
building blocks of nucleotides combine to form nucleic acids
enables them to carry information, as the letters of an alphabet
combine to form words.

4. Building Units of Genome

5. BASIC STRUCTURE OF
NUCLEOTIDES

6. SUGAR
(PENTOSES)
Present in RNA Present in DNA
Ribose and
Deoxyribose differ
in structure at C-2.
Deoxyribose has one
oxygen less at C-2
as compared to
ribose.

7. PHOSPHATE GROUP
Phosphate group is a
polar molecule due to the
presence of highly ionized
oxygen atoms.

8. NITROGENOUS BASES
The nitrogenous bases found in nucleotides are aromatic
heterocyclic compounds.

9. The bases are of two types.
1. Purines
• Two ring structure (Fused ring)
• A six-membered organic ring plus a five-membered ring
Example: Adenine and Guanine
2. Pyrimidines
• Single six-membered ring
Example: Cytosine, Thymine, Uracil
PURINES & PYRIMIDINES

10. MAJOR BASES IN NUCLEIC ACIDS
(6-aminopurine)
(2-amino 6-oxypurine)
(2,4-dioxy-5-methylpyrimidine)
(2-oxy-4-aminopyrimidine) (2,4-dioxypyrimidine)

12. FORMATION OF POLY NUCLEOTIDES

13. • Specific purine-pyrimidine couples are called complementary
base pairs.
• Chemical attractions called hydrogen bonds hold the base pairs
together.
• Two hydrogen bonds join A and T, and three hydrogen bonds
join G and C. This is a universal rule which is applied in the
structure of DNA.
• In case of RNA, thymine is replaced by uracil.
COMPLIMENTARY BASE PAIRING

15. Nucleoside vs Nucleotide
• Nucleoside consists of a nitrogenous base covalently attached to a
sugar (ribose or deoxyribose) but without the phosphate group.
Nucleoside = Nitrogenous base + Sugar
• A nucleotide consists of a nitrogenous base, a sugar (ribose or
deoxyribose) and one to three phosphate groups.
Nucleotide = Nitrogenous base +Sugar + Phosphate

16. NUCLEOTIDE VS NUCLEOSIDE

17. FUNCTIONS OF NUCLEOTIDES
• Nucleotides and their derivatives are biologically abundant
substances that participate in nearly all biochemical
processes.
• Units of nucleic acids
• Play central roles in both the storage, the expression and
transmission of genetic information
• Energy metabolism, protein synthesis and control of enzyme
synthesis.
• Nucleotides are structural components' of some coenzymes
e.g. NAD and FAD
• cAMP and cGMP are second messengers for some hormonal
actions
• GTP and GDP are involved in a cascade of signal transduction

18. LECTURE II
STRUCTURE OF DNA & RNA
13 April 2024 18

19. Learning Objectives:
• Structure of DNA- Watson-Crick Model
• Structure of RNA
• Difference between DNA & RNA
• DNA to RNA - Central Dogma of life

20. Amazing Molecule of Life!
DNA was discovered in
1869 by Johann
Friedrich Miescher, a
Swiss researcher.
DNA contained genetic
material was first made
in 1944 by Avery,
Macleod and MacCarty.

21. The Watson-Crick Model:
DNA is a double helix
• 1951 – James Watson learns about x-ray diffraction pattern
projected by DNA.
• DNA consists of two molecules that are arranged into a ladder-
like structure called a Double Helix.
• A molecule of DNA is made up of millions of tiny subunits called
Nucleotides.
• Each nucleotide consists of:
• Phosphate group
• Pentose sugar
• Nitrogenous base

22. STRUCTURE OF DNA

23. A Single DNA Strand

24. DNA consists of two chains of nucleotides-
Double Helix

25. DNA consists of two chains of nucleotides-
Hydrogen bonding
• Hydrogen bonds hold the
nitrogenous bases of one
strand to the nitrogenous
bases of the second strand .
• Note that the sugars point
in opposite directions—that
is, the strands are
antiparallel.

26. Antiparallel nature of DNA strands
One-half of the double helix runs in
a 5′ to 3′ direction, and the other
half runs in a 3′ to 5′ direction.
The opposing orientation of the
two nucleotide chains in a DNA
molecule is called Anti-parallelism.

27. Complimentary Base Pairing in DNA
The symmetrical DNA double
helix forms when nucleotides
containing A pair with those
containing T, and nucleotides
containing G pair with those
carrying C.

28. CHARGAFF'S RULE OF BASE PAIRING
The rules of base pairing explain the phenomenon that
whatever the amount of adenine (A) in the DNA of an
organism, the amount of thymine (T) is the same.
Similarly, whatever the amount of guanine (G), the amount of
cytosine (C) is the same.
A = T and C = G.

29. DNA CONFORMATIONS
• DNA exists in several conformations.
• The most common conformation found so far is B-DNA.
There are three conformations of DNA.
1. B-DNA: right-handed double helix with a wide and narrow
groove.
2. A-DNA: major groove is very deep and the minor groove is
quite shallow.
3.Z-DNA: consists of dinucleotides, each with different
conformations.

31. DENATURATION OF DNA
Denaturation of DNA can be done by two ways.
1. In vivo i.e. inside the living system
2. In vitro i.e. in the laboratory

32. The two strands of DNA can be separated or unwind during DNA
replication, RNA transcription and genetic recombination.

33. • In the laboratory the separation of two strands of DNA can be
done by
1. Changing the pH
2. Heating
• During denaturation hydrogen bonds between bases breaks and
the base pair separates when DNA is treated above a certain
temperature or melted.
• The temperature at which DNA is half denatured is called
melting temperature, Tm of DNA.

36. STRUCTURE OF RNA
The building blocks of RNA are Nucleotides,
just like DNA.
A Nucleotide in RNA is made of 3 important
components:
1. Ribose sugar (instead of Deoxyribose)
2. Phosphate
3. Nitrogen base
There are 4 nitrogen bases in RNA (A,G,C, and
U that pair together)
A  U C G

37. • RNA is single stranded and does not have to stay in the nucleus!
• RNA is not found in chromosomes because it does not carry the
genetic code, however it can read the DNA code and take the
information out of the nucleus.
• RNA’s main function is to build proteins!

38. STRUCTURE DIFFERENCE BETWEEN DNA & RNA

39. Types of RNA
1. Messenger RNA (mRNA):
Copies a portion of unzipped DNA in the nucleus.
Codes for proteins
2. Ribosomal RNA (rRNA):
mRNA carries the message to the ribosome.
Forms ribosome core for translation.
3. Transfer RNA (tRNA):
Adaptor between mRNA & amino acids.
Attaches the proper amino acids at the ribosome.

41. Relationship b/w DNA and RNA

42. LECTURE III
CENTRAL DOGMA OF MOLECULAR
BIOLOGY

43. FLOW OF GENETIC INFORMATION

44. 44
DNA TO RNA- Central Dogma of Life
The central Dogma defines the most important basis of
molecular biology that:
Genes are units propagating themselves and
functioning through their expression in the
form of proteins.
• To use the genetic information in the nucleus to synthesize
proteins, the process of transcription first makes a copy of
a gene that is an RNA molecule complementary to one
strand of the DNA double helix.
• The RNA copy is taken out of the nucleus and into the
cytoplasm. There, the process of translation uses the
information in the RNA to manufacture a protein by
aligning and joining specified amino acids.
• Finally, the protein must fold into a specific three-
dimensional form in order to function.

45. CENTRAL DOGMA OF MOLECULAR
BIOLOGY

84. PROTEIN SYNTHESIS

88. 1. In transcription, a
portion of DNA unzips and
mRNA composes a strand
complementary to the DNA
template.
Every three bases of mRNA is
known as a CODON.
Next, mRNA exits the nucleus,
moving to a ribosome in the
cytoplasm
2. In translation , the
anticodon of transfer rna
attaches the proper amino acid
to make a specific protein.
This universal triplet or three
base amino acid code consists
of 20 amino acids that make up
proteins.

89. 89
Protein synthesis

90. GENETIC CODE