Presented By:

Aqsa Ayoub

Kinnaird college for

women lahore

GENETIC

FINGERPRINTING

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Introduction

• A technique used to distinguish between

individuals of the same species using only

samples of their DNA

• The process of DNA fingerprinting was

invented by Alec Jeffreys at the

University of Leicester in 1985.

• He was studying the gene of myoglobin.

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Genetic fingerprinting Process

Sampling

Blood

Hair

Saliva

Semen

Body tissue cells

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RESTRICTION FRAGMENT LENGTH

POLYMORPHISM

1. DNA EXTRACTION

• Cells are broken down to release DNA

2.DNA CUTTING

• The DNA is cut into fragments usingrestriction enzymes.

• Each restriction enzyme cuts DNA at aspecific base sequence.

• The sections of DNA that are cut out arecalled restriction fragments.

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Contd…….

3.FRAGMENTS SEPERATION

• Fragments are separated onthe basis of size using a processcalled gel electrophoresis.

• DNA fragments are injectedinto wells and an electriccurrent is applied along thegel.

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Contd…..

• DNA is negatively charged so it isattracted to the positive end ofthe gel.

• The shorter DNA fragments movefaster than the longer fragments.

• DNA is separated on basis of size

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Contd…

4.DNA TRANSFER

• DNA split into single strandsusing alkaline solution

• DNA fragments transferred fromgel to filter paper or nylonmembrane

• (This is called Southern blotting)

• Gel, with filter paper attached, isremoved & separated

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Contd….5. ANALYSIS

Radioactive probe in solution

binds to DNARevealing a pattern of bands

X-ray film 8

PCR analysis

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Short Tandem Repeats (STR) analysis• STR: repeated sequences of 3-5 base pairs (loci) which can be

identified in a known data base.

• Very useful in DNA analysis because they show great variability among individuals.

• Newer and more precise method yielding errors of about 1 in 1029.

• Does not require very much DNA, can be coupled with PCR.

• Short tandem repeat (STR) technology : evaluates specific regions (loci) that are found on DNA.

• The variable (polymorphic) nature of STR regions intensifies the discrimination between one DNA profile and another. 10

CHANCES OF A MATCH

….there is a chance of 1 in 10 that this

fragment occurs in many individuals…

Suppose that…………

…and.there is a chance of 1 in 20 that this

fragment occurs in many individuals…

…and.there is a chance of 1 in 10 that this

fragment occurs in many individuals…

…and.there is a chance of 1 in 30 that this

fragment occurs in many individuals, but…

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Probability of a match

…the probability of all 4 bands matching in any person other thanthe suspect is

1 in 10 x 1 in 20 x 1 in 10 x 1 in 30

= 1 in 10 x 20 x 10 x 30 That is 1 in 60,000

When a larger number of bands is involved, the probability that the suspect is not guilty becomes one in many thousands*

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AmpFLP

• AmpFLP, or amplified fragment length polymorphism put into practice during the early 1990s.

• This technique was also faster than RFLP analysis and used PCR to amplify DNA samples.

• It relied on variable number tandem repeat (VNTR) polymorphisms to distinguish various alleles,

• Which were separated on a polyacrylamide gel using an allelic ladder (as opposed to a molecular weight ladder).

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Contd…• Bands could be visualized by silver staining the gel.

• In addition, because the analysis is done on a gel, very high number repeats may bunch together at the top of the gel, making it difficult to resolve.

• AmpFLP analysis can be highly automated, and allows for easy creation of phylogenetic trees based on comparing individual samples of DNA.

• Due to its relatively low cost and ease of set-up and operation, AmpFLP remains popular in lower income countries.

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Applications

Forensic Science

Family Relationships

Health Care

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Thank you

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