2. Outlines
• Introduction
• DNA
• DNA structure
• RNA
• RNA structure
• What are the difference between DNA and
RNA?
• Questions
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3. Introduction
• In 1869, Friedrich Meischer was the first
scientist to identify and isolate the DNA
as a distinct molecule ( he named it
“nuclein" this isolation was DNA with
associated proteins extracted from cell
nuclei).
• In 1953, James Watson and Francis Crick
described the structure of DNA as a
Double Helix model.
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4. Deoxyribo Nucleic Acid/DNA
• DNA is an acidic substance present in nucleus.
• Double-helix structure.
• Found in Nucleus/chromosomes.
• It acts as the genetic material that carries the
genetic information.
• It is made up of Nucleotides (it is the basic
building block of nucleic acids).
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7. Deoxyribo Nucleic Acid Structure
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• The two strands are
coiled in a right-handed
fashion(Clockwise).
• The pitch of the helix is
3.4 nm.
8. Deoxyribo Nucleic Acid/DNA Structure
• Double-helix structure with
two right handed helical
polydeoxyribonucleotide
strands twisted around the
same central axis (diameter
of double helix is 2 nm).
• The two strands are
antiparallel.
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9. • The two polynucleotide chains, where the
backbone is constituted by sugar-phosphate,
and the bases project inside.
• The phosphodiester linkages of one of these
strands run in 5′ to 3′ direction while the other
strand runs in 3′ to 5′ direction
• The genetic information is present only on one
strand known as template strand.
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Deoxyribo Nucleic Acid Structure
10. • The double helix
structure contains major
and minor grooves in
which proteins interact
with DNA.
• Nucleotides are linked
together by covalent
bonds called
phosphodiester linkage
(Sugar to Sugar).
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Deoxyribo Nucleic Acid Structure
11. • These two strands are held together by
hydrogen bonds ( C≡G , A = T), other forces
e.g., hydrophobic interactions between
stacked bases are also responsible for stability
and maintenance of double helix.
• Glycosidic bond Between Sugar and Base.
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Deoxyribo Nucleic Acid Structure
14. What is the Nucleotide of DNA?
Each nucleotide has three components:
1. Phosphate group.
2. Pentose Sugar {Deoxyribose (in the case of
DNA)}.
3. Single Nitrogen Base {the purines (adenine [A]
and guanine [G]), each with two fused rings, and
the pyrimidines (cytosine [C], thymine [T], and
uracil [U]}.
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15. 15
The Nitrogenous Bases of DNA
Nitrogenous
bases
Pyrimidine Purine
Thymine
Cytosine
Adenine
Guanine
16. RiboNucleic Acid/RNA
• RNA is one of the three major
macromolecules (along with DNA and
proteins) essential for all known forms of life.
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17. RiboNucleic Acid/RNA
• Ribonucleic acid (RNA) is a molecule similar to
DNA.
• Ribonucleic Acid (RNA) is found mainly in the
cytoplasm of the cell although it is usually
synthesized in the nucleus.
• RNA is a single-stranded molecule Helical in
structure.
• It has a much shorter chain of Nucleotides.
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19. Nucleotide of RiboNucleic Acid/RNA
• Each Nucleotide has three components:
1. Phosphate group.
2. Pentose Sugar (Ribose).
3. Single nitrogen base {the purines (adenine
[A] and guanine [G]), each with two fused
rings, and the pyrimidines (cytosine [C], and
uracil [U]}.
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20. 20
The Nitrogenous Bases of RNA
Nitrogenous
bases
Pyrimidine Purine
Uracil
Cytosine
Adenine
Guanine
23. Questions
• Name the pentose sugar in RNA and DNA?
• Write out the full name of the Nitrogen base
given by the following:
T=
C=
A=
G=
U=
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24. 1. In double helix of DNA, the two DNA strands show
which type of characteristics?
a) coiled around a common axis
b) coiled around each other
c) coiled differently
d) coiled over protein sheath
2. A nucleotide is formed of which of the following
units?
a) nitrogen base and phosphate
b) nitrogen base, sugar and phosphate
c) nitrogen base and sugar
d) sugar and phosphate
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Questions
25. Qs
3. Which of the following nitrogenous base is not present
in RNA?
a) adenine
b) thymine
c) cytosine
d) guanine
4. To which of the following does thymine form hydrogen
bonds in DNA?
a) adenine
b) thymine
c) cytosine
d) guanine
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26. • To which of the following does guanine form hydrogen
bonds in DNA?
a) adenine
b) thymine
c) cytosine
d) guanine
• The nitrogenous base is linked to the ribose or
deoxyribose sugar via a
a. Glycosidic bond
b. Amide bond
c. Hydrogen bond
d. Phosphodiester bond
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Qs
