DNA FINGER PRINTING

Who Invented it?

DNA fingerprinting was developed in 1984 by Alec. J. Jeffrey at the University of Leicester

•WHAT IS DNA FINGER PRINTING?

A technique used by scientists to distinguish between individuals of the same species

using only samples of their DNA

• It was used first to discover genetic diseases but now is also used to help catch criminals

This method of identification is useful in many

applications such as forensics, paternity testing, and molecular archeology

DNA fingerprinting has revolutionized the way the world identifies biological matches

• DNA fingerprinting may also be used as a system of personal identification as well as used for medical purposes in detecting and curing genetic diseases.   

The basis of DNA profiling is the use of Restriction Fragment Length Polymorphisms (RFLPs).

Single base changes may create or delete specific restriction sites in DNA.

These changes are visualized by isolating the DNA, cutting it with a specific restriction nuclease, separating the fragments by size on a gel, then detecting a specific fragment by hybridization to a complementary probe.

Preparation of a DNA fingerprint Step 1Specimen collection

blood, semen, etceasy to contaminate a DNA sample with

DNA from other sources (bacteria, DNA of person collecting sample)

DNA is not stable for very long-it degrades sunlight heat moisture

STEP 2 : ISOLATION OF DNA• Cells are broken down to release DNA.

• If only a small amount of DNA is available it can be amplified using the polymerase chain reaction (PCR).

PCR amplification of DNA

1 strandof DNA

Heat todenaturedouble-strandedDNA

Design primers that anneal to STR locus

Amplify all the regions of the chromosomewhere the STRs exist.

STR locus

STR locus

PCR allows you to make millions of copies of the STR region from a single copy of DNA you recovered from crime scene.

STEP 3: CUTTING,SIZING AND SORTINGSpecial enzymes called restriction enzymes

are used to cut the DNA at specific places Each restriction enzyme cuts DNA at a

specific base sequence.

The sections of DNA that are cut out are called restriction fragments.

This yields thousands of restriction fragments of all different sizes because the base sequences being cut may be far apart (long fragment) or close together (short fragment).

STEP 4 :

Fragments are separated on the basis of size using a process called gel electrophoresis.

DNA fragments are injected into wells and an electric current is applied along the gel.

A radioactive material is added which combines with the DNA fragments to produce a fluorescent image.

Transfer of DNA to nylon

The distribution of DNA pieces is transferred to a nylon sheet by placing the sheet on the gel and soaking them overnight

In order to find a specific VNTR sequence on a single strand of DNA, a probe made from the complementary sample sequence must be labeled with aradioactive compound.

The probe is then able to bond to the DNA, and by using the radioactive tag on the probe, the location of the attached probe may be identified.

LABELLING OF DNA

A visual signal is produced when the different probes anneal (bind) to the complementary sequence in the DNA sample

Practical Applications of DNA Fingerprinting 1.Paternity and Maternity person inherits his or her VNTRs from his or

her parents Parent-child VNTR pattern analysis has been

used to solve standard father-identification cases

No longer necessary with PCR technology

PCR amplification, then DNA fingerprinting

2. Criminal Identification and Forensics DNA isolated from blood, hair, skin cells,

or other genetic evidence left at the scene of a crime can be compared

FBI and police labs around the U.S. have begun to use DNA fingerprints to link suspects to biological evidence – blood or semen stains, hair, or items of clothing

Simpson/Goldman MurderPretrial hearings announced that blood

collected at crime scene matched that of O.J.sDefense argued that contamination could have

occurred during sample collection and between collection of different samples

Technician admitted mislabeling samplesPossibility that evidence might be tainted was

obvious to both the court and the juryDNA evidence was not allowed as evidenceWhen rules of evidence are not followed, DNA

samples lose their value in court.

3. Personal Identification The notion of using DNA fingerprints as a

sort of genetic bar code to identify individuals has been discussed

4.Diagnosis of Inherited Disorders diagnose 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.Developing Cures for Inherited Disorders By studying the DNA fingerprints of

relatives who have a history of some particular disorder

identify DNA patterns associated with the disease

6.identification of Chinese medicine The Hong Kong Baptist University was

able to use DNA fingerprinting to identify the Chinese medicine—Lingzhi in 2000

6.MOLECULAR ARCHEOLOGY•“Tyrolean Ice-Man”, who was found inthe Alps, and the mummies of Egypt found in the dry desert.

•The ice man was found tobe around 5300 years old, and DNA was extracted from the remains of his gut whichfound small traces of food that he ate (Ice Man, 2005).

•This was one of the most historicarcheological discoveries in the last century.

DNA evidence has shown that the majority of bison herds have some domestic livestock as ancestors.No outward (phenotypic) evidence that

this is the case, however.

COMBINED DNA INDEX SYSTEM

CODIS identifies 13 markers, plus Amelogenin (AMEL) to determine sex:[2]

CSF1PO D3S1358 D5s818 D7s820 D8S1179 D13s317 D16s539 D18s51 D21s11 FGA THO1 TPOX vWA These markers do not overlap with the ones commonly used for 

genealogical DNA testing. Some may be indicative of genetic diseases.[3]

[edit]Indices and database structure

DNA FINGER PRINTS MAY ONE DAY BE OUR NATIONAL

ID CARDS