DNA fingerprinting is a technique used to identify individuals by analyzing polymorphisms in their DNA. It was developed in the 1980s by Alec Jeffreys in the UK. The technique involves isolating DNA from samples like blood or hair, digesting it with restriction enzymes, and comparing polymorphic loci between individuals to determine a match. DNA fingerprinting can be used to identify criminals, victims, and solve paternity disputes through analyzing variable number tandem repeats in the genome.

1. DNA FINGERPRINTING
PREPRED BY: VIPIN KUMAR SHUKLA

2. (INTRODUCTION)
 DNA fingerprinting is the technique to establish the
identity of victims (Murder, Accidents, Criminals) with
the help of blood stains, Semen stains, Hair roots, Tears or
Saliva, etc.
 This technique was developed by “Alec Jeffery's (1985-
86) and his colleagues in U.K.
 DNA fingerprinting of an individual is the description of
specific alleles present at a series of polymorphic loci of
the genome.

3. CONTD…..
 A polymorphic locus is that region of genomic DNA
whose sequence is different in different individuals.
 DNA fingerprinting is the most sensitive and most popular
technique in Forensic science in identifying criminals in
cases of rape, murder and solving paternity disputes.
 It is also called as DNA Profiling.
 The polymorphism of different DNA sequences is studied
either as RFLP or by PCR amplification.

4. CONTD…..
 The study includes polymorphism of minisatellites,
microsatellite and minivarient repeats (MVR).
 These sequences together are called variable number of
tandem repeats (VNTR).
 They are end to end duplications of identical or almost
identical sequence of (2-80 bases)
 They are dispersed throughout the genome and constitute
hypervariable dispersed repetitive sequence.

5. STEPS OF DNA
FINGERPRINTING

6. RFLP ANALYSIS
 This is based on probe hybridization.
 It includes study of Multilocus Polymorphism
(MLP) and Single Locus Polymorphism (SLP).
 For this analysis the genomic DNA is isolated
from the blood stains, semen stains or hair roots,
etc. and then this is hybridized with specific
DNA probes.

7. CONTD……
 This process involves:
 Digestion of genomic DNA with a selected restriction
enzyme.
 Separation of DNA segments by Agarose gel
electrophoresis.
 Denaturation of DNA fragments by alkali treatment.
 Transfer of single stranded DNA onto a Nylon membrane
(i.e., blotting of DNA.
 Fixation of separated DNA fragments to the membrane by
exposing to UV light.

8. IMAGES SHOWING THE DNA
FINGERPRINT OF SEMEN STAIN

9. CONTD….
 DNA fragments are hybridized to specific DNA probes.
 The DNA probes correspond to the hypervariable
minisatellites in DNA.
 These have tendem repeats of short sequence ranging from
(1 to 20kb).
 A large number of these minisatellites are scattered
throughout the human genome.
 These attribute polymorphism in DNA and have a stable
inheritance.

10. CONTD…..
 The probes used may be Multilocus or single
locus and are represented as MLPs and SLPs
(Multilocus probes and Single locus probes).
 In case of MLP analysis hybridization takes
place not only between the probe and DNA
fragments strictly complementary to it but also
with those fragments that have similar related
sequences.
 As a result many different fragments are
detected.

11. SLP ANALYSIS
 In case of SLP analysis, probe hybridizes with
DNA fragments of only that VNTR locus, which
has exactly the same sequence of repeat units as
that of the probe.
 As a result, which has exactly the same sequence
of repeat units as that of the probe.
 As a result, just two bands develop in each lane
of the gel.
 In case of MLP analysis only one hybridization
and detection is needed but in SLP method, the
same process repeated four or more times.

12. PCR ANALYSIS OF STRS
 DNA fingerprinting by probe hybridization of
polymorphism of VNTR sequences needs relatively large
amounts of DNA which may not be available in many
cases.
 Also it is doubted that there may be chances of unrelated
individuals having same or very similar fingerprinting.
 Therefore STR sequences are obtained by PCR
amplification and are used for DNA fingerprinting.

13. CONTD….
 Each STR in human population may have as many as ( 10)
different alleles.
 These alleles differ in the number of tandem repeats of
short sequence repeat unit.
 The two primers used for PCR anneal to the unique DNA
sequences located outside the STR sequence.
 The product of the PCR are subjected to Agarose gel
electrophoresis.
 The amplification products of different STR alleles s
distinct bands.

14. IMAGES OF MINISATELLITE DNA IN
DNA FINGERPRINTING

15. PCR METHOD
 The PCR method can produce results from very
minute amount of DNA from the site of crime.
 PCR can also be used for Minisatellite variant
repeat (MVR).
 It works on the basis of variation within the
sequence of repeat unit and the variation in the
numbers of repeat units.

16. PCR AMPLIFICATION TECHNIQUEFOR
ANALYSING STR LOCUS

17. INTERPRETATION OF RESULTS
 In MLP analyses, the bands obtained from DNA recovered
from the crime scene, are completed with the bands from DNA
of suspects.
 The probability of two individuals sharing the complete MLP
profile will be (0.25n) where n is the total number of bands.
 In case of SLP analysis the molecular weight of matching
bands is measured.
 The frequency of molecular weight of each locus is completed
for each allele of each SLP locus.

18. APPLICATIONS OF DNA
PROFILING
 DNA fingerprinting or DNA profiling is applicable for
following :
 It enables identification of criminals and victims of crime
or accidents.
 Kinship analysis: It is used to infer the blood relationship
in the members of the same family.
 Paternity dispute: DNA fingerprinting is used in
determining whether a given male is father of a given
child.

19. CONTD…..
 Parentage Determination: In case of lost child, is
possible to determine the actual parents.
 Sex of an Individual: In sex of badly damaged
bodies of accident victims or of archaeological
specimens, can be identified by DNA profiling.