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JAWAHAR NAVODAYA VIDYALAYA
MAMNOOR WARANGAL
BIOLOGY PROJECT
Topic: DNA
PREPARED BY:
GUIDED BY: shri.g.v.NARSAIYYA(SIR)

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CERTIFICATE
This is to certify that this project is bonafide work
done by master/kumari of class XII
bearing HALL TICKET NO: During
the academic year 2019-2020 for the fulfilment of
AISSCE-2020 BIOLOGY PRACTICALS in
JAWAHAR NAVODAYA
VIDYALAYA,MAMNOOR,WARANGAL(D),
TELANGANA.
Signature of the student
Signature of Internal Examiner
Signature of External Examiner
Signature of the Principal

3.
B.POORNIMA
ACKNOWLEDGEMENT
At the outset I express my indebtness to the authorities of
NVS for providing me the opportunities for studying in
JAWAHAR NAVODAYA VIDYALAYA, MAMNOOR,
WARANGAL,TELANGANA.
I am very much delighted and feel privileged to place on my
sincere gratefulness to Principal Smt.B.POORNIMA of our
vidyalaya for providing facilities and extending help
concerned to this project work.
I take this opportunity to express my deep sense of gratitude
to Shri.G.V.NARSAIYYA(SIR) ,PGT-BIOLOGY of
suggesting the project,valuable guidance and constant
encouragement to carry out this project work.
I also thank Shri.M.V.SHIVA REDDY,PGT-IT &
MD.ESA,FCSA of our vidyalaya for me in completion of the
project.
I also thank MOGILI, lab attendant of our vidyalaya.

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Signature of the Student
THE DNA:
DNA is deoxyribonucleic acid. It is located in nuclei
of cells. Which make up the body, consequently DNA can be
considered as one of the building blocks of the body. DNA is
the hereditary material that lies within the nucleus and is
called nuclear DNA.
However, small portion of the DNA also be found in the
mitochondria and is called Mitochondrial DNA.
HISTORY OF THE DNA RESEARCH
 The history of the DNA research began with Gregory
Mendel the “Father of Genetics.” He had performed an
experiment with plants in 1857 that lead to increased
interest in study of Genetics. His experiment form the
basis from the basis of Genetics and gave a fair idea of
inheritance.

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• Friedrich Miescher and Richard Altman- Friedrich
Miescher (1844-1899) discovered a substance he called
“Nuclein” in 1869, later he isolated a pure sample of the
material now known as DNA from the sperm of the
salmon, and in 1869 his pupil, Richard Altman named it
“nucleic ace” these substance was found to exist only in
chromosomes.
• Frederic Griffin- Frederic griffin a scientist , was
working on a project in 1928 that formed the basis that
DNA was the molecule of inheritance.
From the experiment Griffin speculated that the killed
virulent bacteria had passed on a characteristic to the non-
virulent one to make it virulent. He believed these
characteristics was in the inheritance.
• Oswald Avery- Oswald Avery continued with Geritance
molecule. This passing on of the inheritance molecule
was what he called transformation. griffin experiment
around a dacade late to see what the inheritance
molecule was. In this experiment he destroyed the lipids,
ribonucleic acids, carbohydrates, and proteins of the
virulent pneumonia. Transformation still occurred after
this, next he destroyed the DNA, transformation did not
occurs. He had found the basis of the inheritance.
• Phoebus Levene - In 1929 Phoebus Lenene at Rockfeller
Institute identified the components that made up a DNA
molecule. These are 1] Four bases- (a)adenine,

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(b)guanine, (c)cytosine, (d)thymine 2]
Sugar; 3] phosphate
• Erwin Chargaff’s rule- he found the pattern in the
amounts of the four bases: adenine, guanine, cytosine,
thymine. A=T and G=C this discovery late become
Chargaff’s rule
• Maurice Wilkins and Rosalind Franklin- Maurice tried to
made a crystal of the DNA molecule. They wanted to
take x-ray pictures of the DNA to understand how KNA
works. These two scientist were successful and obtained
an x-ray pattern. The pattern appeared to contain rungs,
like those on a ladder between to strands that are side by
side. They found that DNA had a helix shape.
• Watson and Crick- in 1953, two scientists, James Watson
and Francis Crick, were trying to put together a model of
DNA. They took a look at Franklin and Wilkins pictures
of the x-ray and made their model they created a model
that has not been changed much since then. Their model
sowed a double helix with little rungs connecting the two
strands. These rungs were the bases of a nucleotides .
They also fund that if they paired thymine with adenine
and guanine with cytosine DNA would look uniform.
This pairing was also in accordance with Chargaff’s rule.
They also fund that a hydrogen bond could be formed
between the two pairs of base. In addition each side is a
compete complement of the other.

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 Alec Jeffrey's – DNA profiling was developed a few
years later in 1984 by English Geneticist Alec Jeffrey of
the university of Leicester and coas first used to conceit
Colin pitchfork in 1988 in the Ender by murders case in
Leicestershire, England. These began the journey of
DNA research.
STRUCTURE OF DNA
 The DNA is a polymer molecule with four types of basic
chemical, these are called the deoxyribonucleotides.
 They contain- a sugar (deoxyribose) negatively
charged phosphate group the base adenine, guanine,

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cytosine, thymine the nucleotides are linked together by
covalent phosphodiester bond.
• DOUBLE STRANDE HELIX- while looking at the
structure, Watson and crick found that DNA is a double
stranded helix or a ladder that is twisted. Here the bases
form the rungs of the ladder and sugar phosphates are on
the outside.
• They are hydrogen bonds between a large purine base (A
or G) on one strand and a small pyrimidine (T or C) on
the other chain. The base pair sequence is usually
referred to as the primary structure of DNA this
sequences determines the actual structure of the DNA.
• SHAPE AND HARDNESS OF DNA- DNA can
have a variety of shapes and lengths under physiological
conditions DNA is found in the so called B-form, a right-
handed double-stranded helix. There is repeat twist or
helix after every 10.4 base pairs or around 34
nanometers. The thickness of the DNA is about 2nm and
a base pair thickness is about 0.34nm.
• DNA Grooves- As the DNA strands are twisted they
are twisted they have distinct grooves. DNA has two
kinds of grooves that play important roles in its
functioning. Major and minor groves help in formation
of different proteins. These grooves bind proteins lead
transcription factors that lead to formation of the of
proteins.

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• CONFOMATIONS OF DNA- DNA can be present in
several different conformations and these are important
for DNA functions and actions. Conformations of DNA
are vital for the repair of damaged DNA because they act
with the enzymes in the body.
• DNA SUPERCOILING- The DNA strand are like a
phone cable or a rope. This coiling is a central property
of DNA. DNA can be in a relaxed or a coiled state.
• Coiling helps the extremely long DNA strand to fit into
the tint cell nucleus. Put simply the supercoiling property
makes DNA more efficient packing in more information
in small spaces.
SALIENT FEATURESOF DNA DOUBLE HELIX-
It is made of two polynucleotide chains. Where
the backbone is constituted by sugar-phosphate, and the bases
project inside
• The two chains have anti-parallel polarity. It means if
one chain ha the polarity 5’-3’, the other has 3’-5’ .
• The bases in two strands are paired through hydrogen
bon forming base pairs. Adenine form two hydrogen
bonds with thymine from opposite strand and vice-versa.
• Similarly, Guanine is bonded with cytosine with three H-
bonds. As a result, always a purine comes opposite to a
pyrimidine. This generates approximately uniform
distances between the two strands of the helix.

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• The two chains are coiled in a right-handed fashion. The
pitch of the helix is 3.4nm and there are roughly 10 bp in
a helix is each turn. Consequently the distance between a
bp in a helix is approximately equal to 0.34nm.
• The plane of one base pair stacks over the other in
double helix. This, in addition to H-bonds confers
stability of the helical structure.
DNA PROCESSES: A] REPLICATION
• DNA replication is the process by which a double
stranded DNA molecule is copied to produce two
identical DNA molecules. Replication is an essential
process because whenever a cell divides the two new
daughter cells must contain the same genetic
information, or DNA, as the parent cell.The replication
initiates at specific points called origins where the DNA
double helix is unwound.A short segment of RNA called
a primer is then synthesized and acts as a starting po9int
for new DNA synthesis. an enzyme called DNA
polymerase nest begins replicating the DNA by matching
bases to the original strand,once synthesis is
complete,the RNA primers are replaced with ,
• Any gaps between newly synthesized DNA segments are
sealed together with enzymes,DNA replication is crucial
process therefore to ensure that mistakes or mutations are
introduces the cell proofreads the newly synthesized

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DNA. once the DNA in a cell is replicated the cell can
divide into two cells, each of which has an identical copy
of the original DNA.
DNA POROCESSS: 2] TRANSCRIPTION
• Transcription is the process by which the information in
a strand of DNA is copied into a new molecule of
messenger RNA (mRNA) .
 DNA safely and stably stores genetic material in the
nuclei of cells as a reference or template. Meanwhile,
mRNA is comparable to a copy from a reference book
because it carries the same information as DNA but is
not used for long term storage and can freely exit the
nucleus. Although the mRNA contains the same
information. It is not an identical cop of the DNA
segment, because its sequence is complement to the

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DNA template.
Transcription is carried out by an enzyme
called RNA polymerase and a number of accessory
proteins called transcription factors.
• Transcription factors can bind to specific sequences
called enhancer and promoter sequences in order to
recruit RNA polymerase to an appropriate transcription
site. Together, the transcription factors and RNA
polymerase form a complex called the transcription
initiation complex. this complex initiates transcription,
and the RNA polymerase begins mRNA synthesis by
matching complementary bases to the original DNA
strand. The mRNA molecule is elongated and once the
strand is complexly synthesized, transcription is
terminated.
• The newly formed mRNA copies of the gene then serves
as blueprints for protein syntheses during the process of
translation.
DNA PROCESSES: TRANSLATION
• Translation is the process by which a protein is
synthesized from the information contained in a
molecule of mRNA. During translation an mRNA
sequence is read using the genetic code, which is a set of
rules that define how an MRNA sequence is to be
translated into the 20 letter code of amino acids, which
are the building blocks of proteins. The genetic code is a
set of three letter combination of nucleotides called

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codons, each of which corresponds with a specific amino
acid or stop signal. Translation occurs in a structure
called the ribosome which is a factory for the synthesis
of proteins. The ribosome has a small and a large subunit
and is a complex molecule composed of several
ribosomal RNA molecules and a number of proteins.
• Translation of an mRNA molecule by the ribosome
occurs in three stages: initiation, elongation and
termination. During initiation the small ribosomal
subunit bind to molecule carrying the amino acid
methionine bind to what Is called the strand codon of
mRNA sequence. The start codon in all mRNA
molecules has the sequence AUG and codes for
methionine. Nest, the large ribosomal subunit binds to
form the complete initiation complex. During the
elongation stage, the ribosome continues to translate each
codon in turn. Each corresponding amino acid is added to
the growing chain and linked via bond called a peptide
bond. Elongation continues until all of the codons are
read.
• Lastly the termination occurs when ribosome reaches a
stop codon (UAA, UAG, UGA) . Since there are no Tran

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molecules that can recognize these codons, the ribosome
recognizes that transcription is complete. The new
protein is then released, and translation complex comes
apart.
CHEMISTRY OF DNA
• The DNA is negatively charged molecule. It has a
phosphate backbone that gives it the negative charge.
This property is important when samples with DNA are
subjected to testes like electrophoresis.
• DNA is soluble in water. It is generally stored in a
buffered solution in lab. A buffer contains chemical
buffer Tris (to control PH) and the chelating agent EDTA
that helps trap cofactors for enzyme that can attack DNA
• DNA is insoluble in ethanol or purified alcohol.
• DNA can be denatured and renatured. Denatured is
essentially opening up of the strands f the DNA with
heat. While renaturation the strands cool off and rebind
with each other.
• DNA absorption of ultraviolet light- DNA absorbs UV
light. The bases of the DNA called purine and pyrimidine
bases absorb light srongley in the UV range with most
absorption at 260nm.

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DNA EVOLUTION
• DNA is the only biomolecule that has been constantly
changing over millions of years and yet maintains a basic
patter that carries a record of life’s evolution on earth.
DNA evolves over millions of years continuously
dividing, this what makes each species unique.
DNA RECOMBINATION
• DNA sequence in cells are maintained from generation to
generation with very little change. While this is true,
where is evidence that the DNA sequence in
chromosomes does change with time and the DNA gets
rearranged over time.
• The combination of the genes on the genome may
change due to such DNA rearrangements. In a
population, this sort of genetic variation is important to
allow organisms to evolve in response to a changing
environment. These DNA rearrangements are caused by
a class of mechanism called genetic recombination.
MUTATION AND DNA CHANGE
• Copying error or accidental damage or permanent
changes in the structure of DNA are called
mutations.Mutation is the DNA often the information it
encodes. Sometimes these mutation may lead bacteria to
become resistant to antibiotics that are used to kill
them.In humans, mutations are often detrimental. These

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may be responsible for thousands of inherited diseases
and mutation that appear in cells throughout the lifetime
of an individual. These may lead to many types of
cancer.DNA repair thus becomes important to prevent
mutations and inherited dislikes.
DNA AND TECHNOLOGY
• DNA and molecular biology has advanced by leaps and
bound. It has found use in Pharmacology, genetic
engineering in disease prevention, in increasing
agricultural growth, in detection of disease and crime
(Forensics) etc.
Advanced fields du to DNA technology-
1]Forensics, 2]Bioinformatics,
3]pharmacology&Nanotechnology,4]Archaeology
&Anthropometry.
• DNA technology in Forensics- DNA is unique because it
is unique. The ability to examine DNA found at a crime
scene is very useful Forensic tool.
• The common methods are to identify and describe the
DNA profile includes Restriction fragment Length
Polymorphism [RELF] and Short Tandem Repeat
Profiling [STR].
 DNA IN BIOINFORMATICS- over the last
decades there has been rapid progress the human
genome project and biotechnologies. These advances

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result in many complex datasets associated within
depth knowledge, e.g. Genome sequences of many
species, microarray expression profiles of different cell
lines. Single nucleotide polymorphism (SNPs) or
mutations in the human genome, etc. This has given
birth to a new field of Bioinformatics and has vast
utility in the Pharmaceutical industry.
• DNA IN THE ARCHAEOLOGY AND
ANTHROPOMETRY- The analysis of DNA extracted
from archaeological specimens can be used to address
anthropological questions. This helps in tracking DNA
evolution, migratory patterns and species evolution over
the ages.
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