1. Advanced Level Teacher’s
Seminar-2006
DNA Finger printing and
Related techniques
S.Santharooban
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2. DNA Fingerprinting or DNA
Typing
• Method to identify the DNA of an individual
• DNA is unique to a person, no two individuals
have identical DNA except identical twins or
clones
• All the cells of a person has same DNA
• A specimen for DNA fingerprinting can be any
type of cell
– Blood, saliva, sperm, muscle, teeth, bones or any DNA bearing
cell
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3. Importance of VNTRs
• DNA contain exons and introns.
• Exons that contain genetic information.
• Introns supply no relevant genetic information at all
• Introns contain repeated sequences of
base pairs.
• These sequences is called Variable
Number Tandem Repeats (VNTR).
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4. • VNTRs contain anywhere from 20 to 100 base
pairs.
• Every human being has some VNTRs.
• To determine if a person has a particular VNTR,
a Southern Blot is performed.
• In this technique, VNTRs is probed, through a
hybridization reaction, with a radioactive
version of the VNTR in question.
• The pattern which results from this process is
often referred to as a DNA fingerprint.
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5. Southern Blot technique
involves…
Invented by Prof. Ed. Southern.
• Extract DNA from the sample of an individual
• Digest into small fragments using restriction enzyme
• Separate DNA fragments by gel electrophoresis.
• Denature the DNA,
• the entire DNA is changed as single-stranded.
5. Apply a sheet of nitrocellulose paper to the gel
(containing DNA).
6. Make to permanently attach the DNA to the sheet.
7. The Southern Blot is now ready to be analyzed.
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6. • Apply a radioactive genetic probe/ a
radioactive version of the VNTR to
nitrocellulose filter paper.
• Radioactive probe bind to target
sequence/VNTRs.
• Washed out excess probe.
• Determine the position of the bounded probe
by autoradiography.
» By an X-ray filming
» areas where the radioactive probe binds will show up on
the film.
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8. Bands resulted from
electrophoresis
Specific probe
Original sample of DNA Final bands resulted from
Southern blotting
PCR can also be used in the DNA fingerprinting techniques. In case,
where the DNA sample in question, is too small, then the PCR
techniques is used to amplify the DNA present in it.
Discussed later 8
9. Use of DNA fingerprinting
• Criminal Identification and Forensics.
» used in forensic medicine-confirm the suspect
• Determine family relationships
» paternity confirmation, family diseases
• Applicable to both plants and animals
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10. Polymerase Chain Reaction
(PCR)
• Invented by Kary. B. Mullis.
• used to amplify specific regions of a DNA strand.
• sample is crushed and added different buffers
solution and primers.
• Then it is put into Thermocycler to amplify the
DNA strands using appropriate temperature.
• The following reaction take place in the
amplification.
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11. Single strand formation at 94-980C
Annealing at 680C with
primers
Elongation at 720C (P=
Polymerase)
First cycle complete.
The two resulting DNA strands make up the
templates for the next cycle. Thus, amount o
DNA duplicated in each cycle.
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12. What will happen to double stranded DNA if
the temperature is raised to 900C????
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15. • Then Ethidium bromide is added to stain the DNA.
• poured onto the electrophoresis gel.
• allowed to run nearly for 1 hrs.
• It results in series of bands.
• Bands are laid down based on the base pairs of each type of DNA.
• Bands present in the distal end of application consist the DNA of
less base pairs.
• Bands present in the proximal end of application consist the DNA of
higher base pairs.
• In between are moderate base pairs.
• Obtained bands will be compared to references banding
pattern.
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