DNA and RNA are nucleic acids that are essential for life. DNA contains the genetic instructions used in the development and functioning of all living organisms. It is a double-stranded molecule found in the nucleus of cells. RNA is a single-stranded molecule that helps carry out the instructions specified by DNA, such as synthesizing proteins. The four bases found in DNA are adenine, guanine, cytosine, and thymine, while RNA contains adenine, guanine, cytosine, and uracil. Watson and Crick discovered that DNA has a double helix structure in 1951. Their model showed how the bases on each strand are paired through hydrogen bonding in a complementary way.

1. DNA
&
RNA

2. SYNOPSIS
• History
• Structure of Nucleic acid
• Structure of DNA & RNA
• Watson and crick’s model of DNA
• Types of DNA
• Types of RNA
• DNA VS RNA
• Conclusion

3. HISTORY
 In 1869, friedrich Miescher
 Nuclein
 With the help of RICHARD ALTMAN in 1889
(Protamine)
 In 1879,Phoebus Aaron Theodore
Levene
 He characterized the different forms
of nucleic acid, DNA from RNA,
 and found that DNA contained Sugar
molecule and a phosphate group
 In 1878, Albrecht Kossel isolated the non-
protein component of "nuclein", nucleic
acid, and later isolated its five
primary nucleobases.
 In1951, Francis
Crick with James
Watson gives the
structure of DNA

4. Nucleic acid
BIOPOLYMERS made up of Monomers.
These monomeric units are known as NUCLEOTIDES.
PHOSPHATE
SUGAR
BASE

5. SUGAR
 5 carbon sugar hence pentose
 RIBOSE & DEOXYRIBOSE

6. PHOSPHATE
 Same molecule present in ATP
 It is a polar molecule due to presence of
highly ionized oxygen atoms

7. NITROGENOUS BASE
 Molecules in which orgnanic chemicals
combines with nitrogen and act as base
 As they can donate electrons and forms new
molecules
 The nitrogen combines with other atoms to
form a ring structure.
 PURINES AND PYRIMIDINES
 DOUBLE RING SINGLE RING
 LARGER SMALLER
 6CARBON RING 9CARBON RING

8. SUGAR
BASE
Glycosidic
bond
PHOSPHATE
Ester bond

9. Sugar
Phosphate
backbone
Hydrogen bond
COMPLIMENTARY BASE PAIRING

10. WATSON AND CRICK’S DNA MODEL
• The DNA polynuleotide chain has form of a regular helix.
• It has diameter of about 20 A.
• The helix complete turn at every 34 A along its length.
• The internucleotide distance is 3.4 A consist a stack of 10 nucleotides.
• The sugar-phosphate backbones remain on the outside, while the core of
the helix contains the purine and pyrimidine bases.
• The DNA helix has a shallow groove called minor groove and a deep groove
called major groove
• The two strands are antiparallel i.e. they ran in opposite directions so that
the 3′ end of one chain facing the 5′ end of the other.

11. Types of DNA
 B-DNA
 A-DNA
 Z-DNA

12.  B-DNA
• The most common and predominate type of structural conformation of DNA in
cell
• B-DNA is a right handed helix.
• Each base pair in B-DNA has same width.
• The helical diameter of B-DNA is 20A.
• Each turn on helix in B-DNA posses a height of 34A.
• Each turn in the B-DNA consists of 10 base pair and the internucleotide distance
between these bases is 3.4A.
• Major groove of B-DNA is wide and deep,and minor goove is narrow and deep.

13.  A-DNA
• A-DNA is formed from B-DNA under dehydrating condition.
• A-DNA is much wider and flatter than B-DNA.
• A-DNA is also right handed
• The helix diameter is 26A.
• A-DNA contain11.6 base pairs per turn.
• The distance between the adjacent base pairs 2.9A.
• A-DNA has narrow and deep major grooves,and minor grooves of A-
DNA is wide & shallow.
• A-DNA is 20-25% shorter than B-DNA due to smaller rise per turn.
• It has an axial hole at the centre.

14.  Z-DNA
• The Z-DNA is a left handed helical structure,
• The double helix winds in a zig-zag pattern.
• The helical diameter is 18A.
• The height of helix turn is 18A.
• Each helical turn of Z-DNA contains 12 nucleotides.
• The distance between each nucleotide is 7.4A.
• Z-DNA posses a more or less flat major groove and minor groove is narrow
and deep.
• It has solid core at the centre.

15. Types of DNA

16. Types of RNA
m-RNA
r-RNA
t-RNA

17. 2. Messenger RNA (mRNA):
• Messenger RNA is a linear molecule transcribed from one strand of DNA.
• It carries the base sequence complementary to DNA template strand. The base sequence of
mRNA is in the form of consecutive triplet codons.
• Length of mRNA depends upon the length of polypeptide chain it Codes for. Polypeptide
length varies from a chain of a few amino acids to thousands of amino acids.
• m-RNA acoounts for just 5%of the total RNA in the cell.
• Eukaryotic mRNA is quite stable and survives from a few minutes to more than a day. In
mammalian RBC, through the nucleus is lost, mRNA continues to produce haemoglobin for
many days.

18. 3. Ribosomal RNA (rRNA):
• Most of the RNA of the cell is in the form of ribosomal RNA which constitutes about
85% of the total RNA.
• Ribosomes consist of many types of rRNA. The 70S ribosome of prokaryotes, in its
smaller subunit of 30S has 16S rRNA. The 50S larger subunit consists of 23S and 5S
rRNA. Similarly 80S ribosome has 18S rRNA in its smaller subunit of 40S. The 60S
larger subunit has 28S, 5.8S and 5S rRNA.
• The rRNA plays major role in protein synthesis. They interact with mRNA and tRNA
at each step of translation or protein synthesis.
• The rRNA molecules form complexes with specific proteins in ribosomes. The RNA-
protein complexes are called ribonucleoproteins (RNP).

19. 1. Transfer RNA (tRNA):
• It delivers amino acids to ribosome and decodes the information of mRNA.
• The tRNA plays the role of an adaptor and matches each codon to its particular
amino acid in the cytopolasmic pool.
The tRNA has two properties:
(a) It represents a single amino acid to which it binds covalently.
(b) It has two sites. One is a trinucleotide sequence called anticodon, which is
complementary to the codon of mRNA. The codon and anticodon form base pairs
with each other. The other is amino acid binding site.
The tRNA charged with an amino acid is called amino acyl tRNA.

20. 1. Amino acid arm:
• It has a seven base pairs stem formed by base pairing between 5′ and 3′ ends of tRNA. At 3′ end a sequence of 5′-
CCA-3′ is added. This is called CCA arm or amino acid acceptor arm. Amino acid binds to this arm during protein
synthesis.
2. D-arm:
• Going from 5′ to 3′ direction or anticlockwise direction, next arm is D-arm. It has a 3 to 4 base pair stem and a loop
called D-loop or DHU-loop. It contains a modified base dihydrouracil.
3. Anticodon arm:
• Next is the arm which lies opposite to the acceptor arm. It has a five base pair stem and a loop in which there are three
adjacent nucleotides called anticodon which are complementary to the codon of mRNA.
4. An extra arm:
• Next lies an extra arm which consists of 3-21 bases. Depending upon the length, extra arms are of two types, small extra
arm with 3-5 bases and other a large arm having 13-21 bases.
5. T-arm or TψC arm:
• It has a modified base pseudouridine ψ. It has a five base pair stem with a loop.
• There are about 50 different types of modified bases in different tRNAs, but four bases are more common. One is
ribothymidine which contains thymine which is not found in RNA. Other modified bases are pseudouridine ψ,
dihyrouridine and inosine.

21. DNA VS RNA
Comparison DNA RNA
Name DeoxyriboNucleic Acid RiboNucleic Acid
Function Long-term storage of genetic information;
transmission of genetic information to make
other cells and new organisms.
Used to transfer the genetic code from the
nucleus to the ribosomes to make proteins. RNA
is used to transmit genetic information in some
organisms and may have been the molecule used
to store genetic blueprints in primitive
organisms.
Structural Features B-form double helix. DNA is a double-stranded
molecule consisting of a long chain of
nucleotides.
A-form helix. RNA usually is a single-strand helix
consisting of shorter chains of nucleotides.
Composition of Bases and Sugars deoxyribose sugar
phosphate backbone
adenine, guanine, cytosine, thymine bases
ribose sugar
phosphate backbone
adenine, guanine, cytosine, uracil bases
Propagation DNA is self-replicating. RNA is synthesized from DNA on an as-needed
basis.
Base Pairing AT (adenine-thymine)
GC (guanine-cytosine)
AU (adenine-uracil)
GC (guanine-cytosine)
Ultraviolet Damage DNA is susceptible to UV damage. Compared with DNA, RNA is relatively resistant
to UV damage.

22. Conclusion
RNA and DNA are very similar in structure. For example both includes phosphate groups
and nitrogenous bases.two important differences are that DNA uses sugar deoxyribose
while RNA uses closely related sugar ribose.
In addition DNA uses the bases A,G,C,T while RNA uses A,G,C,U.
THYMINE of DNA is shielded by methyl group which gives extra stability whereas RNA
has URACIL without any protecting group. And also double strands of DNA gives extra
strength,thus DNA is most suited as a hereditary material than RNA molecule.

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24. Reference
• Cell biology by PS VERMA
• Lehninger-Principle of biochemistry
• Fundamental of biochemistry by J.L.Jain