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Harsh Vardhan Dna Fingerprinting
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Transcript of Harsh Vardhan Dna Fingerprinting
DNA FINGERPRINTING
HARSH MOONAT CLASS XII “A”
What is DNA Fingerprinting?
A technique used by scientists to distinguish between individuals of the same species using only
samples of their DNA. It is also known as DNA PROFILING
Why DNA Fingerprinting?
The chemical structure of everyone's DNA is the same. The only difference between people (or any animal) is the
order of the base pairs. The information contained in DNA is determined primarily
by the sequence of letters along the zipper. Using these sequences, every person could be identified
solely by the sequence of their base pairs (except identical monozygotic twins)
There are millions of base pairs, the task would be very time-consuming. Instead, scientists are able to use a shorter DNA Fingerprinting method, because of repeating patterns in DNA.
These patterns do not, however, give an individual "fingerprint," they are able to determine whether two DNA samples are from the same person, related people, or non-related people.
Historical background
• DNA fingerprinting was developed in 1984 by Alec. J. Jeffrey at the University of Leicester
• He was studying the gene of myoglobin.
• Dr. V.K. Kashyap and Dr. Lalji Singh started the DNA fingerprinting technology in India
Alec. J. Jeffrey
Principle of DNA Fingerprinting
DNA carries a short repetitive sequences of nucleotides which do not code for proteins and specific for each person.
These sequences are called variable number of tandem repeats (VNTR's) or minisatellite.
In DNA Fingerprinting VNTR are used as probe because of its high degree of polymorphism.(polymorphism is the occurrence of inheritable mutations in a population at high frequency)
Biological materials used for DNA fingerprinting
Blood
Hair
Saliva
Semen
Body tissue cells
Bone
Steps of DNA Fingerprinting
Step ONE : Isolation of DNA
Isolation of DNA from a nucleus and purification by chemical method or
centrifugation.
Steps of DNA Fingerprinting
Step TWO: Amplification
If only a small amount of DNA is available it can be amplified using the
polymerase chain reaction (PCR)
Steps of DNA Fingerprinting
Step Three: digestion
The DNA is cut into fragments using restriction enzymes which cuts DNA at a specific base sequence.
The sections of DNA that are cut out are called restriction fragments.
Steps of DNA Fingerprinting
Step Five: Southern blotting
The distribution of DNA pieces is transferred to a nylon or
nitrocellulose sheet by placing the sheet on the gel and soaking them
overnight. ( Edwin Southern : A Biochemist)
Steps of DNA FingerprintingStep Four: Separation of DNA
Fragments
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.
DNA is negatively charged so it is attracted to the positive end of the gel.
The shorter DNA fragments move faster than the longer DNA fragments. DNA is separated on basis of size.
Steps of DNA Fingerprinting
Step Seven: Autoradiography
An X-ray film is developed for this binding pattern and a photographic
copy of the DNA bands is obtained. This pattern is called
DNA Fingerprint.
Steps of DNA Fingerprinting
Step six: Hybridization
Special radioactive DNA probes contains repeated sequences of
bases complementary to those on VNTRs. These radioactive probes
binds to the VNTRs on the nitrocellulose or nylon membrane and produce a fluorescent image.
Practical Applications of DNA Fingerprinting
Paternity and Maternity Tests(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 )
Personal Identification(The notion of using DNA fingerprints as a sort of genetic bar code to identify individuals)
Can someone tell me who is my father?
Practical Applications of DNA Fingerprinting
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 )
Practical Applications of DNA Fingerprinting
Diagnosis of Inherited Disorders and developing cure
(diagnose inherited disorders in both prenatal and newborn babies and by studying the DNA fingerprints of relatives who have a history of some particular disorder identify DNA patterns associated with the disease)
Study of Evolution(Find out relationship between various
races of human beings and study of organisms facing danger of extinction)
DNA Fingerprinting (AT A GLANCE) DNA sections with repeating sequences are called VNTRs and
are used in DNA fingerprinting. No DNA fingerprint test can prove defendant's guilt, but a
match can establish probability. A fingerprint begins with a sample of tissue such as blood,
skin, or semen. Fingerprinting can also be used to determine paternity and to
identify victims of disasters or war. It was developed in 1984 by Alec. J. Jeffrey. N……….? Gel electrophoresis separates the DNA fragments by size, as
the smaller pieces move faster through the gel. E……………? Restriction enzymes break DNA into more manageable sizes
for fingerprinting. PCR technique is used to amplify tiny amount of DNA. R………..? Indian government funded the Centre for DNA Fingerprinting and
Diagnostics (CDFD). N………….? T……………?
HOTS Questions1. HGP provides detailed information about genetic
constitution of an individual, then why DNA fingerprinting is used in criminal cases and paternity disputes?
2.VNTR does not code for any protein yet they are important in DNA fingerprinting?
3. What is DNA polymorphism?
4. If insufficient amount of DNA found from a crime scene, how amount of DNA could be increases?
5. Differentiate repetitive DNA and satellite DNA.
6. During investigations of a criminal case it was found that DNA fingerprints of two suspicious individuals was exactly similar. How it can be possible?
REFERENCESNCERT Text book of Biology (XII)
Comprehensive Biology (XII)
Truman’s elementary Biology +1
Madhuban a text book of Biology part 2
Modern’s abc of Biology XII
Internet