Forensic Sciences and DNA Fingerprinting

LECTURE 22:

Biotechnology; 3 Credit hours

Atta-ur-Rahman School of Applied Biosciences (ASAB)

National University of Sciences and Technology (NUST)

Forensic Science

• Forensic biology is the application of biology to law enforcement

• The analysis of the biological or genetic properties of evidence for identification

• It is used to establish identity in criminal investigation, in case of disputed paternity, or in historical or archaeological research

The Genetic Basis of Identity

1. Fingerprints2. Retinal Scan3. Blood Typing4. DNA Fingerprinting

1- Fingerprints

• Finger prints are the classic example of a phenotype used in law enforcement

• They are due to the variation in the pattern of dermal ridges, small skin elevation on your fingers

Fingerprints

• Fingerprints pattern depends on more than one gene• They are multigenic• This create huge genetic diversity underlying this

phenotype • One could expect fingerprints of twins identical, but

they are not• Minor variation happens because of environmental

factors• This science is being used for identification by late

1800

2- Retinal Scan

• Retinal scan provide a more high tech form of unique identification

• It take advantage of unique pattern of blood vessels on the retina on the back side of eye

Retinal Scan

• Scanning typically take about a minute• Several scans are required• Infrared light is used for this job, because blood

vessel on the retina absorb this better than the surrounding tissue

• A computer algorithm is used to convert this scan into digital data

• There are about 10 fold more information on retinal scan than in fingerprints

Applications

• Application in high security system• CIA, FBI, NASA and prison system• Now it is being employed on animal

identification• Fingerprinting in many security system and

also in law enforcement system (crime secene)

3- Blood Typing

• Blood typing has been used in the courtroom for more than 50 years

• Other body fluids i.e. Sweat, tears, urine, saliva and semen also have cells with surface proteins that can be analyzed

• RBC contain many proteins and lipids for the identification

Blood Typing

• Galactose transferase• N-acetylgalactosamine

transferase

Blood Typing

Inheritance of ABO blood system

4- What is a DNA fingerprint?

• DNA profiling (also called DNA testing, DNA typing, or genetic fingerprinting) is a technique employed by forensic scientists to assist in the identification of individuals by their respective DNA profiles.

• DNA profiles are code sets of numbers that reflect a person's DNA makeup, which can also be used as the person's identifier.

• It is used for parental testing and crime investigation.

DNA fingerprint Profiling Analysis

a) RFLP Analysisb) PCR Analysisc) STR Analysisd) AmpFLP Analysise) Mitochondrial DNA Analysisf) Y-chromosome DNA Analysis

a. RFLP Analysis

b. PCR Analysis

c. STR Analysis

PCR Analysis

Paternity Testing

PCR amplification, then DNA fingerprinting

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Offspring STRs

Mother’s STRs

STRs of suspected Father

Is the suspect the father?

d. Genealogies by Mitochondrial & Y-chromosome DNA Analysis

• Genealogy is the study of families and the tracing of their lineages and history

• Mitochondrial DNA is maternally inherited and often used to specifically trace maternal ancestry

• Y chromosome can be used to trace male ancestry

Genealogies by Mitochondrial & Y-chromosome DNA Analysis

• It is possible to submit personal samples of DNA for analysis to companies such as Oxford ancestor

• Their matri-Line service allows persons of European decedent to trace their maternal ancestry back to one of seven ancestral females

• Y-chromosome follows a paternal pattern of inheritance.

• The Y-chromosome contain many STR sequence in non-coding region.

• Y linked STR loci are specific to Y-chromosome• They find useful application in forensic

analysis in case of sexual assault.

Genealogies by Mitochondrial & Y-chromosome DNA Analysis