DNA fingerprinting forensic microbiology

Ppt of DNA fingerprinting and applications

1. DNA Fingerprinting

2. DNA Fingerprinting
Applications
• To link a suspect to a crime scene and for criminal exonerations.
O.J. Simpson and Colin Pitchfork
• I.D. Missing persons or Dead Person.
• Link a suspect to an event.
Clinton – Lewinsky Scandal
• Paternity Cases.

3. DNA Fingerprinting Applications
DNA fingerprinting is routinely used to
test samples of blood, hair root,
saliva and other bodily fluids.

4. DNA Fingerprinting
Why is DNA an Indispensable Tool in Forensics Science?
Study into the structure of the human genome has led
to the discovery that portions of DNA structure of
certain genes are as unique to each individual as
fingerprints.

5. What is DNA?
In 1953 James Watson & Francis Crick discovered the structure
Deoxyribonucleic Acid – DNA.
It is found in the nucleus of all living cells, with the exception of
Red Blood Cells.
Double Helix Structure

6. What is DNA?
• A person has 46 chromosomes, over 100,000 genes, 3 billion bases of DNA.
• Each leg of the ladder in the double helix consists of alternating
sugar and phosphate units.
• The nucleotide bases consist of the following:
Adenine (A) which pairs with
Cytosine (C) which pairs with
Thymine (T)
Guanine (G)

7. What is DNA?
Replication of a single strand of DNA
A T A G C C A A C C A A
T A T C G G T T G G T T

8. What is DNA?
The order of the bases in a molecule
of DNA provide instructions used to
build proteins.
A piece of DNA that contains all the
information needed to build one
protein is called a gene.

9. What is DNA Fingerprinting?
In 1985 an English geneticist, Alec Jeffreys,
was studying inherited variation within genes
and among individuals.
He studied a genetic peculiarity known as the
intron. Introns are sequences of “junk” DNA
that do not code for a specific protein.
He noticed that some introns are made up of
the same DNA base pair sequences and that
the number of repetitions varies from person to
person.

10. DNA Fingerprinting Techniques
• Restriction Fragment Length Polymorphisms – RFLP are the repetitive
intron fragments
RFLP
• How RFLP works:
• DNA from several individuals was “cut” with a restriction enzyme.
• The “cut” DNA is sorted by size.
RFPL animation

11. DNA Fingerprinting Techniques
Disadvantages of RFLP
• Expensive.
• Requires a large sample size.
RFLP (continued)
• Time consuming.
• Labor intensive
Advantages of RFLP
• Very confident in results
example:
Using RFLP on a sample of
blood from the O.J. Simpson
murder trial said the chances
someone other than Simpson
left their DNA at the crime
scene was 1 in 6 Billion.

12. DNA Fingerprinting Techniques
PCR
• Polymerase Chain Reaction – PCR.
• A technique used to “copy” DNA.
• Can be used with minute amounts of DNA.
• Uses DNA’s natural replication process to multiple sample size.
PCR animation

13. DNA Fingerprinting Techniques
PCR (continued)
Disadvantages of PCR
• Results are not as impressive
as RFLP.
Advantages of PCR
• Small sample size needed.

14. DNA Fingerprinting
The Power of DNA Fingerprinting
Several drops of O.J. Simpson’s blood were found
at the Nicole Brown-Simpson and Ronald Goldman
crime scene. Both RFLP and PCR tests were performed. Here are the
official results:
PCR (3 Drops of Blood were tested)
1/240,000 chance blood belonged to someone other than O.J. Simpson.
Drop #1: 1/170 Million chance blood belonged to someone other than O.J. Simpson.
RFLP (2 Drops of Blood were tested)
Drop #2: 1/57 Billion chance blood belonged to someone other than O.J. Simpson.
Source: Criminalistics, An Intro to Forensics Science, Richard Saferstrein

15. DNA Fingerprinting
A picture of DNA fingerprinting

16. DNA Fingerprinting
Mitochondrial DNA
• Another structure in the cell that contains DNA is the
mitochondria.
• Each cell contains thousands of
mitochondria, each containing several
Loops of DNA.
• Unlike nuclear DNA, this DNA is only
inherited from your mother.
• This makes any individual with the same
maternal lineage indistinguishable.

17. DNA Fingerprinting
How DNA is used to determine Paternity
• DNA fingerprinting can be used to determine a child’s parents.
• We know you receive 50% of you nuclear DNA from mom, and
the other 50% from dad.

18. DNA Fingerprinting
Interpret the results of the following
DNA fingerprints
•Both daughter 1 and son 1 share
genes with mom and dad, while
daughter 2 has genes of mom but
not the dad, and son 2 does not
share genes with either parent.

19. What is CODIS?
• CODIS is an acronym for:
Combined DNA Index System
• Administered by the FBI, system which stores DNA of
certain convicted felons.