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Submitted To: Mrs
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It is an organic compound that has a unique molecular structure
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Definition:
Deoxyribonucleic acid (abbreviated DNA) is the polynucleotide molecule that carries genetic information for the
development and functioning of an organism
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Where is it Located?
Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found
in the mitochondria (where it is called mitochondrial DNA or mtDNA)
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They marked a milestone in the history of science and gave rise to modern
molecular biology, which is largely concerned with understanding how genes control the chemical processes within
cells
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Deoxyribose (a pentose sugar)
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Phosphate

Nucleotides:
Nucleotide is a chemical compound formed by glycoxidation of a nitrogen base with a pentose sugar and its
esterfication is by one to three phosphoric acids
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Hydroxyls groups provide reactivity enabling phosphoric acid to combine with the
sugars and help in condensation reactions
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Free hydroxyl groups pass hydrogen to
the medium with their oxygen atom becoming negatively charged
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Therefore, it has more energy than a covalent bond
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Both of them occur in furanose state or pentagon ring with one oxygen and four cabon
atoms
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Carbon atom contains two hydrogen atoms
in deoxyribose
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The remaining structure is similar in both with hydroxyl group attached to carbon 1’,3’ and 5’ and
CH2OH group connectwd to acrbon 4’
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Ribose sugar is found in nucleotides forming RNA and anumber of other compounds like
AMP, ADP, ATP etc
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Nitrogen bases are of
two types- Purines and Pyrimidines
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The common pyrimidines are three in number-Thymine, Cytocine and Uracil
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Purines have four nitrogen atoms at 1,3,7 and 9 positions
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Molecular structure of DNA:
The deoxyribose sugar of one nucleotide is joined to joined to the phosphate group of adjacent nucleotide with
glycosidic linkage to form a poly nucleotide chain
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Each base is also attached
to a sugar molecule and a phosphate molecule
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Nucleotides are arranged in two long strands that form a spiral called a double helix
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Features of DNA:
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DNA consists of helix in which two polynucleotide chains and are about same axis
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Backbone of each chain which consists of alternate sugar-phosphate residues(hydrophilic) are on the outside
of the helix facing the surrounding
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34 nm apart in DNA helix
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4 nm, therefore, in each
helical turn, 10 bases are present
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The helix has two external grooves, the narrow groove is called minor groove while the wide groove is called
as major groove
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The minor grooves often are site for
binding small molecules
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In one strand the
direction is 5’-3’ while in the opposite one it is 3’-5’
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There is H- bonding between bases
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The two strands are held together by their bases
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Similarly, cytosine (a pyrimidine) lies opposite to guanine (a
purine)
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Base pairing or purine pyrimidine association is essential as the nitrogen bases are not of the same size
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7A) than the pyrimidines C and T (3
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Functions:
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Nucleotides are precursors of the nucleic acids, DNA and RNA
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Gene Therapy: Defective heredity can be rectified by incorporating correct genes in place of defective ones
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DNA controls the metabolic activities of the cell through protein synthesis
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DNA along with protein histone forms the chromosome
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It is the heterocatalytic activity of
DNA
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The amount is small
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It is located in the cytoplasm
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Organelles having DNA are absent
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DNA occurs in highly supercoiled state
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Extra DNA segments occur in the cytoplasm
in the form of plasmids
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C-G content is generally more than A-T
content
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It is commonly circular, occasionally linear
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There are fewer genes
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The amount is comparatively very large
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Eukaryotic DNA is found inside nucleus, mitochondria and
plastids
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Two types of organelles possess DNA
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Organelle DNA is
naked
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Introns often occur inside the genes
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Content of nonfunctional or repetitive DNA is quite large
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Denaturation separates the two strands in case of nuclear
DNA and tangled mass in case of organelle DNA
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Only one of them does so
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Its complementary strand is named nontemplate strand, plus(+) strand, sense strand or coding strand
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(5’) GCATTCGGCTAGTAAC (3’): DNA nontemplate/ Coding /sense strand
(3’) CGTAAGCCGATCATTG(5’): DNA template/ antisense strand -----→ (5’) GCAUUCGGCUAGUAAC(3’) RNA transcript

Circular and Linear DNA:
In many prokaryotes the two end of DNA duplex are covalently linked to form circular DNA
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In linear DNA, the two sends are free
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CHARGAFF’ S RULE:
Chargaff made observations on various contents of DNA
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Purine And Pyrimidine base pairs occur in equal amount
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Molar quantity of adenine is always equal to the molar amount of thymine
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Sugar deoxyribose and phosphate occur in equimolar proportions
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STRUCTURE OF RNA
RNA Stands for Ribonucleic Acid
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Definition: RNA is one of the major biological macromolecules that are essential for all known forms of life
(along with DNA and Protein)
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This nucleic acid is responsible
for the production of new cells in the human body
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RNA
resembles the same as that of DNA, the only difference being that it has a single strand unlike the DNA which
has two strands and it consists of an only single ribose sugar molecule in it
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RNA is also referred to as an enzyme as it helps in the process of chemical reactions in the body
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A base is attached to
the 1’ position, in generall,
Adenine(A), Cytosine(C)
Guanine(G), Uracil(U)
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Structure Of RNA:

Basic structure of RNA: The ribonucleic acid has all the components same to that of the DNA with only
2 main differences within it
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Adenine and uracil are considered as the major building
blocks of RNA and both of them form base-pair with the help of 2 hydrogen bonds
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Nucleosides are nothing but the phosphate groups which
sometimes also helps in the production of nucleotides in the DNA
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mRNA: Messenger RNA
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tRNA: Transfer RNA

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Based on the
functions, these types of RNA is called the messenger RNA
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In all living cells, the ribosomal RNA plays a fundamental role
in the synthesis and translation of mRNA into proteins
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It is located at the endpoints of each
amino ac

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