Application in Forensics

1. Presentation Topic: Comparison of DNA Typing Methods
M.Talha Iftikhar :15821
Nimra Yasin :45002
Warda Jabbar :45003
Presented to Dr. Muhammad Qasim
BS Biotechnology 5th (Morning)
Government College University, Faisalabad.

2. DNA Typing
“DNA typing is a procedure wherein DNA extracted from a
biological sample obtained from an individual is analyzed”
• The DNA is processed to generate DNA profile.
• This profile is unique for everyone except identical twins.

3. Areas:
• Comparing criminal suspects
• To establish immigration eligibility
• Medical research
• Population genetics
• Paternity Tests
• Property Disputes

4. History of DNA Typing
• First developed in the UK in 1984 by geneticist
“Sir Alec Jeffreys”. Department of Genetics at the
University of Leicester.
• VNTRs were analyzed using RFLP technique.

5. • It was first used in the solving of the murder of two
teenagers, Lynda Mann and Dawn who had been murdered
in Narborough, Leicestershire, in 1986.
• Results were successful innocent was released.
University of Leicester

6. Methods
RFLP
STR
mtDNA
YSTR

7. RFLP
• Restrictions Enzymes are used. Cutting the DNA at
specific recognition sites.
• Formation of different length fragments.
• A large amount of DNA is required. Does not work with
degraded DNA.

8. DNA cut with restriction enzymes is of different lengths
because of
• Deletion of DNA between restriction sites
• Insertion of DNA
• Point mutations in restriction sites
• Variable number of tandem repeats.

9. STEPS
• Extraction: DNA is extracted from cells.
• Restriction Fragments
• Electrophoresis: Agarose gel.
• Transfer DNA to Nylon sheet by soaking them overnight.
• Probing is done by adding radioactive or colored probes
to nylon sheet to produce a pattern called DNA fingerprint.
• DNA Fingerprint is generated.

11. Short Tandem Repeats (STR) Analysis
• STR analysis examines base pairs repeat in specific loci in a
DNA strand.
• They are present in non-coding regions of DNA (98% of
human DNA is non-coding)

12. These can be dinucleotide, trinucleotide, tetranucleotide or
pentanucleotide repeats

13. Benefits
• It can start with a much smaller sample of DNA.
• Markers are highly polymorphic
• The likelihood that any two individuals (except identical
twins) have the same DNA profile is high as 1 in 1 billion,

14. Low Copy Number
“Also called low template (LT) DNA, is the approach where
lower amounts of DNA can be analyzed with STR markers.”
• epithelial cells are shed from the skin.
• DNA from touched cups, gloves, pens etc. can be genotyped.
• FBI has chosen more than 13 specific STR loci to serve as
the standard for DNA analysis.
• Amelogenin gene is also used for male DNA identifications

16. MITROCONDRIAL - DNA
• Mitochondria contains 16kp of genome. Which codes for 37
genes.
• Samples that involve very old bones, teeth or hair.
Used where samples are degraded mitochondrial DNA is
analyzed

17. The non-coding region is called the D-loop, segment of 1200 base
pairs.
Three hypervariable regions in the D-loop (HVI, HVII and HVIII)
analyzed in many research as
population genetics
evolutionary studies
forensic analysis.

19. Advantages
• More sensitive (less DNA needed), degrades slower than nuclear
DNA
• Can be used in cases where nuclear DNA cannot (hair without root,
skeletal remains)
Disadvantages
• All people of same maternal line will be indistinguishable (less
discriminatory)
• More work, more time consuming, more costly

20. Many copies of mitochondrial DNA are present in each cell.
All of a mother’s children have the same
mitochondrial DNA, which is the same as that
of all their relatives in the same maternal line.

21. The Romanov Family
• Ruled Russia for years, overthrown in 1916
• The family was killed by firing squad in 1918.
• Mass grave was discovered in 1991 with four males and five
females, supposedly six females were executed.

22. Nicholas II
1868-1918
Alexei
1904-1918
Olga
1895-1918
Maria
1899-1918
Tatiana
1897-1918
Alexandra
1872-1918
Anastasia
1901-1918

23. • Only nine bodies were found.
• Popular rumor that Anastasia had miraculously been
survived
• Mitochondrial DNA from living and dead (but known
relatives) of the Tsar & his family established that the
remains were indeed theirs
• Nuclear DNA analysis was also done but it was
insufficient.

24. • Anna Anderson continued to claim until her death in 1984
that she was the missing princess, Anastasia
• DNA Proved that she was not a member of the royal
Romanov family and was born to a middle class family in
Poland

25. Y STR
These markers are inherited along a
male lineage, are not subjected to
recombination and are characterized by
a moderate number of polymorphic loci
Analysis of DNA found in one particular chromosome found only in
males, called the Y chromosome
A y-str is a short tandem repeat sequence on Y-chromosome of male.

26. Helpful where there is a mixture of DNA from male and
female contributors.
• if a sample contains a large amount of female DNA and
there is only a small amount of male DNA present, then
examining the Y chromosome gives just the male
contributor’s DNA profile rather than a mixture

27. Forensic DNA testing looks at a set of markers found on specific
chromosomes
Typical STR testing looks at a few markers
on each of many (24) places
Y-STR testing looks at many (23) markers
on just the Y chromosome

28. Uses
• inferring the biological sex of a crime scene
• exclude male suspects from involvement in crime. Whose DNA is
not found.
• population genetics
• highlight multiple male contributors
• Y-STR haplotype analysis is employed in paternity disputes of
male offspring and other types of paternal kinship
• While the Y chromosome isn’t good at distinguishing between
close male relatives. There are always more individuals who
would have the same DNA profile.

29. PCR
• Polymerase chain reaction is used for amplification of DNA
• Kary B. Mullis, developed 1985 and was awarded the Nobel
Prize in 1993.
• Before the PCR amount of DNA needed for analysis was
high.
• Multiplex PCR uses more than 13 markers for STR analysis.
.

30. Requirement
• DNA Template
• Primers
• Deoxynucleoside triphosphates(dNTPs)
• Taq polymeras
• Buffer solution
• Divalent cations(eg.Mg2+)

31. CODIS is the acronym for the Combined DNA Index System
and is the generic term used to describe the FBI's program of
support for criminal justice DNA databases

32. Pcr

33. References
• http://www.dnaforensic.org/dna_typing/dnatyping_1.html
• http://www.exploredna.co.uk/basics-dna-forensics-techniques.html
• https://www.diva-
portal.org/smash/get/diva2:660275/FULLTEXT01.pdf (mtDNA)
• Forensic use of Y-chromosome DNA: a general overview
(Manfred Kayser)
• Y-STR typing in forensic analysis (N. von Wurmb-Schwark a,*, S.
Petermann b , R. Wegener b)