CENTRAL MODEL SCHOOL, BARRACKPORE
SESSION 2024-25
AISSCE, CBSE
BIOLOGY PROJECT FILE
NAME: BIDISHA NANDI
CLASS: 12 SCIENCE
SEC: A
ROLL: 10
AISSCE ROLL NO:
SUBJECT: BIOLOGY
CERTIFICATE
This is to certify that Bidisha Nandi, a student of class XII sec-A,
Roll no.10. has successfully completed her Biology project file under
the guidance of Mrs. Paramita Chatterjee. The entire visit has been
planned and guided by Mrs. Paramita Chatterjee and completed
under her supervision.
Signature: Signature:
External Examiner Internal Examiner
Acknowledgement
I would like to express my thanks to my teacher of Biology, Mrs.
Paramita Chatterjee as well as our respected Principal sir, for giving
me the chance to do this informative and Knowledgeable Project.
Secondly, I would like to thank my parents and my friends without
whose help, the completion of this project within the stipulated
time would have been an impossible task.
Lastly, I express my gratitude to all who have helped me in this
project directly or indirectly.
Yours Sincerely,
Bidisha Nandi
INDEX
Sl. Project name Teacher’s Remarks
no Sign
1. DNA FINGERPRINTING
• Introduction
• Principle of
DNA
fingerprinting
• Methods of
DNA
fingerprinting
• Advantages
and
limitations
• Applications
of DNA
fingerprinting
• Conclusion
• Bibliography
INTRODUCTION
DNA fingerprinting is a technique
that shows the genetic makeup of
living things. It is method of
finding the difference between
the satellite DNA regions in the
genome.”
OR
DNA profiling is a process used to determine the
nucleotide sequence at a certain part of the DNA
that is unique in all human beings.
• The process of
DNA
fingerprinting
was invented
by Sir Alec
Jeffrey at the
University of
Leicester in
1985
Principle of DNA Fingerprinting
The DNA of every human being on the planet is 99.9%
same. However, about 0.1% or 3 x 106base pairs (out of
3 x 109 bp) of DNA is unique in every individual.
Human genome possesses numerous small non-coding
but inheritable sequences of bases which are repeated
many times. They do not code for proteins but make-up
95% of our genetic DNA and therefore called the ―junk
DNA.
They can be separated as satellite
from the bulk DNA during density
gradient centrifugation and hence
called satellite DNA.
In satellite DNA, repetition of bases
is in tandem. Depending upon
length, base composition and
numbers of tandemly repetitive units, satellite DNAs have
subcategories like
microsatellites and mini-
satellites.
Satellite DNAs show
polymorphism. The term polymorphism is used when a variant at
a locus is present with a frequency of more than 0.01 population.
A microsatellite is a repeating sequence of 2-6 base pairs in the
genome. Since it is a type of tandem repeats with short sequences of
nucleotides, microsatellites are also known as short tandem repeats
(STRs). The repeats of single nucleotides are called single nucleotide
polymorphism (SNP). Furthermore, microsatellites occur throughout
the genome. In the human genome, the dinucleotide repeats occur in
every 30, 000 base pairs.
Moreover, microsatellites are a highly
mutative region in the genome. Unique
microsatellite sequences occur within
families. Therefore, we use the analysis of
microsatellites for paternity testing.
Furthermore, the extension of
trinucleotide microsatellite repeats causes severe human disorders
like Fragile X syndrome and Huntington’s disease.
Minisatellite is a repeating sequence
of 10-100 base pairs in the genome.
Here, the repeating unit is
somewhat large and it is called a
DNA motif. Another name for
minisatellite is variable number
tandem repeats (VNTRs). The
number of VNTRs is highly variable
among individuals. The repetitive unit of a minisatellite is GC rich
Due to the highly variable nature of minisatellites among individuals,
scientists use them for DNA fingerprinting. They also use minisatellites
as genetic markers during the linkage analysis.
Some minisatellite sequences are involved in the
formation of RAS oncogene-associated cancer.
Variations occur due to mutations. These mutations in the non-coding
sequences have piled up with time and form the basis of DNA
polymorphism (variation at genetic level arises due to mutations).
The junk DNA regions are thus made-up of length polymorphisms, which
show variations in the physical length of the DNA molecule. At specific
loci on the chromosome the number of tandem repeats varies between
individuals. There will be a certain number of repeats for any specific
loci on the chromosome.
Depending on the size of the repeat, the repeat regions are classified
into two groups. Short tandem repeats (STRs) contain 2-5 base pair
repeats and variable number of tandem repeats (VNTRs) have
repeats of 9-80 base pairs.
Since a child receive 50% of the DNA from its father and the other
50% from his mother, so the number VNTRs at a particular area of the
DNA of the child will be different may be due to insertion, deletion or
mutation in the base pairs.
As a result, every individual has a distinct composition of VNTRs and
this is the main principle of DNA fingerprinting.
As single change in nucleotide may make a few more cleavage site of a
given nucleotide or might abolish some existing cleavage site.
Thus, if DNA of any individual is digested with a restriction enzyme,
fragments pattern (sizes) will be produced and will be different in
cleavage site position.
Methods of DNA Fingerprinting
A. Restriction fragment
length polymorphism
(RFLP)
The first step in this process is to isolate
the DNA from the sample material to be
tested. The sample size for RFLP test must
be large enough to get the proper result.
Once the required size of the sample is
available, the DNA is isolated from the sample
and is subjected to restriction digestion
using restriction enzymes.
The digested DNA sample is then separated
by agarose gel electrophoresis, in which
the DNA is separated based on the size.
The next step is transfer of separated DNA from gel slab onto the
nitrocellulose membrane to hybridize with a labelled probe that is
specific for one VNTR region (radio activity labelled complimentary
sequence for VNTR region nucleotide sequence).
This technique of transferring and hybridizing DNA onto nitrocellulose
membrane is known as southern blotting, a most widely used DNA
detection technique by molecular biologists.
After the hybridization with the
radioactive probes, the X- ray film is
developed form the southern blotting and
only the areas where the radioactive
probe binds will show up on the film. Now
these bands when compared with the
other known samples, will give the final
result of the DNA fingerprinting.
Now these bands when compared with
the other known samples, will give the
final result of the DNA fingerprinting.
Advantages
The RFLP is considered to be more accurate
than the PCR, mainly because the size of the
sample used more, use of a fresh DNA sample,
and no amplification contamination.
Limitation
The RFLP, however, require longer time period
to complete the analysis and is costly.
B. Polymerase Chain Reaction (PCR)
amplification of short tandem repeats (STRs)
Thousands of copies of a particular variable region are amplified by
PCR which the basis of this detection.
STR with a known repeat sequence is amplified and separated using gel-
electrophoresis. The distance migrated by the STR is examined.
For the amplification of STRs using PCR, a short synthetic DNA, called primers
are specially designed to attach to a highly conserved common nonvariable
region of DNA that flanks the variable region of the DNA. By comparing the STR
sequence size amplified by PCR with the other known samples, will give the final
result of the DNA fingerprinting.
Advantages
• Small amount of specimen is sufficient for the test.
• Takes a shorter time to complete.
• Less costly.
Limitation
• Less accurate than RFLP.
• Possibility of amplification contamination.
Applications of DNA
Fingerprinting
DNA Fingerprinting is used by
scientists to distinguish between
individuals of the same species
using only samples of their
DNA. It is a primary method for
identifying an individual.
•Forensic Science: Biological
materials used for DNA profiling are: Blood,
Hair, Saliva, Semen, Body tissue cells etc.
DNA isolated from the evidence sample can
be compared through VNTR (Variable
number of tandem repeats) prototype. It is
useful in solving crimes like murder and rape.
• Paternity and Maternity Determination: A
Person accedes to his or her VNTRs
from his or her parents. Parent-child
VNTR prototype analysis has been used
to solve disputed cases. This
information can also be used in
inheritance cases, immigration cases.
• Personal
Identification: It utilizes the
concept of using DNA fingerprints as a sort
of genetic bar code to pinpoint individuals.
• Diagnosis of
Inherited
Disorders: It is also
useful in diagnosing inherited
disorders in both prenatal and
newborn babies. These
disorders may include cystic
fibrosis, haemophilia,
Huntington’s disease, familial Alzheimer’s, sickle cell anaemia, thalassemia, and
many others.
• Development of
Cures for
Inherited
Disorders: By studying
the DNA fingerprints of relatives
who have a history of some
particular disorder, DNA
prototypes associated with the
disease can be ascertained.
• Detection of AIDS:
By comparing the band of HIV “RNA”
(converted to DNA using RTPCR) with
the bands form by the man’s blood,
person suffering with AIDS can be
identified.
• Breeding Program:
Breeders conventionally use the phenotype
to evaluate the genotype of a plant or an
animal. As it is difficult to make out
homozygous or heterozygous dominance
from appearance, the DNA fingerprinting
allows a fastidious and precise
determination of genotype. It is basically
useful in breeding race horses and hunting
dogs.
Conclusion
DNA fingerprinting has transformed forensic science,
enabling precise identification and solving complex
crimes. This innovative technique leverages genetic
variability, providing invaluable insights in paternity
disputes, genetic research, and identity verification. While
considerations surrounding DNA contamination, sampling
errors, and ethical implications remain crucial, ongoing
advancements in sequencing technologies and
bioinformatics enhance accuracy and efficiency. As DNA
fingerprinting continues to evolve, its impact on justice,
research, and society will expand. Balancing individual
rights with investigative needs, this technology holds
immense potential for advancing truth, justice, and human
understanding.
BIBLIOGRAPHY
•https://nptel.ac.in/courses/102103017/pdf/lec
ture%2038.pdf
•http://www.indiastudychannel.com/resources
/155090-Theprinciples-techniques-
application-DNA-fingerprinting.aspx
•https://www.biologyexams4u.com/2014/05/dn
a-
fingerprintingprocedure.html#.W4QNuPkzbIU
•https://web.wpi.edu/Pubs/E-
project/Available/E-project-011306-
130417/unrestricted/IQP.pdf
•http://www.yourarticlelibrary.com/dna/dna-
fingerprintingprinciples-and-techniques-of-
dna-fingerprinting/12211.
