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9.3 DNA Fingerprinting
KEY CONCEPT DNA fingerprints identify people at the molecular level.
9.3 DNA Fingerprinting
REVIEW from 9.1
• Gel electrophoresis is used to separate DNA fragments by size.– A DNA sample is cut with restriction enzymes.– Electrical current pulls DNA fragments through a gel.
9.3 DNA Fingerprinting
A DNA fingerprint is a type of restriction map.
• DNA fingerprints are based on parts of an individual’s DNA that can be used for identification.– based on noncoding regions of DNA that have
repeating DNA sequences– number of repeats differs between people
9.3 DNA Fingerprinting
A DNA fingerprint is NOT actually a fingerprint! XX
9.3 DNA Fingerprinting
DNA fingerprinting is used for identification.
• DNA fingerprinting depends on the probability of a match.– Many people have the
same number ofrepeats in a certainregion of DNA.
– The probability that two people share identicalnumbers of repeats inseveral locations isvery small.
(mother) (child 1) (child 2) (father)
9.3 DNA Fingerprinting
9.3 DNA Fingerprinting
– Individual probabilities are multiplied to find the overall probability of two DNA fingerprints randomly matching.
– Several regions of DNA are used to make DNA fingerprints.
1 1 1 1500 90 120 5,400,000
1 chance in 5.4 million people to have the same DNA fingerprint
x x = =
1 in every 500 people has 3 copies in location A
1 in every 90 people has 6 copies in location B
1 in every 120 people has 10 copies in location c
9.3 DNA Fingerprinting
• DNA fingerprinting is used in several ways.
– evidence in criminal cases
– paternity tests
(Who da’ Daddy???)– immigration requests– studying biodiversity
– tracking genetically modified crops
9.3 DNA Fingerprinting
Who Ate the Cheese?
• Get into pairs– Each pair needs a Bio book– Read the Royal Incident Report– The restriction enzyme used will always cut between
CCGG – Create you DNA Fingerprint restriction map
Objective: You will examine crime evidence and model the process of gel electrophoresis and DNA fingerprinting to identify the person who ate the Queen’s cheese.
CC GG
