DNA fingerprinting is a technique developed by Alec Jeffreys to identify individuals based on variations in repetitive DNA sequences called minisatellites. Minisatellites have repeat units of 6-100 bases that vary in number between individuals, allowing each person to be uniquely identified. DNA fingerprinting involves using restriction enzymes to cut DNA at specific sites, then analyzing the length of fragments containing minisatellites using gel electrophoresis or Southern blotting to generate a unique fingerprint for each individual. This technique revolutionized forensic science and has applications in paternity testing, population genetics, and criminal investigations.

1. DNA Fingerprinting

2. DNA fingerprinting
• Principles
• Restriction Fragment Length Polymorphism (RFLP)
• Multiplex PCR
• Techniques
• Southern blot
• PCR
• Capillary Electrophoresis
• Population genetics
• Applications

3. Alec Jeffreys
• Molecular geneticist
• Inventor of DNA fingerprinting
• Department of Genetics
University of Leicester
UK
• Original papers
• Jeffreys AJ, Wilson V and Thein SL (1985)
“Hypervariable ‘mini-satellite’ regions
in human DNA” Nature 314, 67-73
• Jeffreys AJ, Wilson V and Thein SL (1985)
“Individual specific fingerprints of
human DNA” Nature 316, 76-79

4. History
Premature
RNA
Exon Exon Exon
Intron Intron
Splicing
Mature
mRNA
DNA
Transcription
Myoglobin gene

5. Repetitive sequence within intron
• Short repeated DNA sequence within intron
• Present in different chromosomal locations
• Unknown functions
• Polymorphism of repeat lengths among individuals arises
from unequal pairing and crossing over between repeats
Simple tandem-repetitive regions of DNA (or 'minisatellites')
Exon Exon Exon
Intron Intron

6. Mini. versus microcomputer
Mini is small…………. but micro is smaller

7. Mini. versus microsatellite
• No. of repeats varies among individuals
• VNTR (Variable Number of Tandem Repeats)
• Minisatellites
• Microsatellites
• Minisatellites
• Repeat unit length – 6-100 bases
• Two to several hundred repeats at each minisatellite
• Thousands of different minisatellites scattered throughout the
genome, but often clustered near the end of the chromosomes –
the telomeres
• Microsatellites
• Repeat unit length: 1-7 bases
• 5 to 100 repeats at each microsatellite
• Thousands of different microsatellites, randomly scattered
throughout genome
http://www.wellcome.ac.uk/en/genome/genesandbody/hg07f006.html

8. Examples of microsatellite
• CACACACACACACACACACACACACACACACACACACA
CACACACACA
• (CA)24
• AATGAATGAATGAATGAATGAATGAATGAATGAATGAA
TGAATGAATGAATGAATGAATGAATGAATGAATGAATG
AATGAATGAATGAATGAATGAATGAATGAATGAATG
• (AATG)28

9. Minisatellites in ONE person
• Similar yet different among minisatellites
• DNA Sequence
• Length of repeats
Similar minisatellites, but different length of repeats
Different minisatellites: different DNA sequence

10. Minisatellites in DIFFERENT individuals
Repeat
length
10 10 30 12 10 40
Repeat
type
A B C D C B
Repeat
length
10 32 15 12 18 20

11. What is DNA fingerprinting?
• Genetic profiling
• A scientific testing process allowing positive identification
between individual DNA
• Alec Jeffreys discovered that minisatellite repetitive DNA
sequences among individuals are:
• Highly polymorphic
• Different repeat lengths among individuals
• Stable within the lifetime
• Inheritable to offsprings
• Measurable by common techniques
• VNTR may be used as a barcode for individuals
• Restriction Fragment Length Polymorphism (RFLP)

12. Applications
• DNA fingerprinting has become an important tool
in forensic investigations.
• used to assess paternity
• study genetic relationships among individual
organisms in natural populations
• Identify specific strains of pathogenic bacteria
• Identify human remains

13. RFLP
EcoRI EcoRI
EcoRI EcoRI
Longer restriction fragment length
Shorter restriction fragment length
Detection of
restriction fragment length
by Southern blot
Note:
Restrictions enzymes may be located within the VNTR, thereby giving multiple bands