DNA fingerprinting is a technique that analyzes variations in repetitive DNA sequences to generate unique profiles that can be used to identify individuals. It involves isolating DNA from samples, digesting the DNA with restriction enzymes, separating fragments via gel electrophoresis, transferring fragments to nylon membranes, probing membranes with radioactively labeled DNA sequences, and comparing band patterns to determine matches. DNA fingerprinting has applications in forensics, paternity testing, diagnosis of inherited disorders, and studying disease-causing genetic variations.

1. DNA FINGERPRINTING–
PRINCIPLE AND APPLICATION
• Presented by-
• SUDIP MAITY
• MSc. 1st seme

2. TOPIC TO DISCUSS :-
WHAT IS DNA FINGERPRINTING ?
PRINCIPLE OF DNA FINGERPRINTING
STEPS / PROCESS
APPLICATION
EXAMPLE
REFERENCES

4.  WHAT IS DNA FINGERPRINTING :-
 DNA fingerprinting is a hybridization
technique used to identify the similarities of
DNA molecule of two individual in the same
species.
 The process of DNA fingerprinting
was invented by Alec Jeffreys in 1985 .

5. The human genome consists of innumerable small noncoding
sequences which are inheritable and repeatedly present. They
can be separated from the bulk DNA as satellite upon
performing density gradient centrifugation and thus known as
satellite DNA. They can be categorized into either
minisatellites or microsatellites depending on the length,
base composition and tandemly repetitive units. These
satellite DNAs show polymorphism and this polymorphism is the
basis of DNA fingerprinting. The repeat regions can be
divided into two groups based on the size of the repeat -
variable number tandem repeats (VNTRs) and short tandem
repeats. These repeats act as genetic markers and every
individual inherits these repeats from their parents. Thus,
every individual has a particular composition of VNTRs and
this is the main principle of the DNA fingerprinting
technique.
 PRINCIPLE OF DNA FINGERPRINTING :-

6.  Biological samples used for DNA
fingerprinting:-
 Blood
 Hair
 Saliva
 Semen
 Body tissue cells……
 Bone
 Teeth
 Sweat

8. Steps of DNA Fingerprinting
There are 9 steps for DNA Fingerprinting
 DNA must be recovered from cells or
tissue. Only a small amount of blood,
hair, or skin is needed to isolate DNA.
STEP 1:- Isolation of DNA

9. STEP 2 :- Extraction of sample
DNA is extracted from the
sample using ‘Proteniase K’
Further phenol- chloroform
extraction and then ethanol
and sodium acetate
precipitation is carried out to
purify the DNA .

10. STEP 3 : Digestion of sample DNA by
Restriction Endonucleases
Special enzyme called restriction endonuclease are
used to digest or cut the sample DNA at a specific
place to form different size.
Example – An enzyme called EcoRI found in
E.coli bacteria ,will cut DNA only when
‘GAATTC’ is occure .
Commonly used RE are ( hae III , Hinf
I, Alu I etc.)

11. STEP 4 : Electrophoretic separation of
different fragments
This digested sample DNA
fragments are separated by gel
electrophoresis.
The gel made from sea weed
agarose (a jelly like product
made by sea weed).
DNA fragment are injected into
wells and an electric current is
applied along the gel.

12. DNA is negatively charged so it is
attracted to the positive end of the
gel.
The shorter DNA fragments move
faster than longer fragments.
DNA is separated on basis of size.

13. STEP 5 : Transfer sample DNA to nylon sheet
The distribution of DNA
pieces are transferred to a
nylon sheet by placing the
sheet on a agarose gel
and soaking them
overnight by the process
of ‘SOUTHERN BLOT’.

14.  STEPS 6: Probing / probe labeling
Minisatellite sequence present in
these fragments are detected or
screened by use of complementary
multiple loci or single locus probe.
As probe are radiolabelled
detection of minisatellite after
hybridization with probes will be
done (southern blot is used)

15.  STEPS 7 : Hybridization
 Labeled probe DNA should be
hybridized with the complementary
sequence located on nylon membrane
for the detection of position of later .
 Membrane is washed to
remove non specific binding
and clearing of the background.

16.  STEPS 8 : Autoradiography / X – ray film
 After the hybridization
with the radioactive
probes , the X- ray films is
developed from the
southern blotting and only
the areas where the
radioactive probe binds
will show up on the film.

17.  STEPS : Interpretation of band patterns
 Analysis of band patterns of different
individual.
Comparison of position of bands.
 Computer software are also
available for the analysis of DNA
fingerprinting

18. 1.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.
2.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.
3.Personal Identification:
It utilizes the concept of using DNA fingerprints as a sort of genetic bar code to pinpoint
individuals.

19. 4.Diagnosis of Inherited Disorders:
It is also useful in diagnosing inherited disorders in both prenatal and
newborn babies. These disorders may include cystic fibrosis,
hemophilia, Huntington’s disease, familial Alzheimer’s, sickle cell
anemia, thalassemia, and many others.
5.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.
6.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.

20. Example :-
 A violent murder occurred.
 The forensics team retrieved a
blood sample from the crime
scene.
 They prepared DNA profiles
of the blood sample, the
victim and a suspect as
follows:

22. REFERENCES:-
1. Basic concept of Recombinant DNA technology , by
DR. Somnath De- principles and steps,
2. http://www.indiastudychannel.com/resource/155090-the
application of DNA finger print.