DNA Fingerprinting. What is DNA Fingerprinting ?. A technique used to identify people using samples of their DNA.
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Every person has two unique fingerprints: the pattern on their fingertips, and the pattern of their DNA. Fingerprints can be altered by surgery, but a person’s DNA fingerprint is the same in every one of their cells. It cannot be altered by any known treatment. Consequently, DNA fingerprinting is rapidly becoming the primary method for identifying and distinguishing among individual human beings.
The DNA is cut into fragments using restriction enzymeswhich cut the DNA at a specific base sequence.
The enzyme EcoRI cutting DNA at the base sequence GAATTC.
DNA fragments are then sorted according to size using a process called gel electrophoresis.
DNA fragments are injected into wells in agarose gel (a jelly-like product made from seaweed) 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 fragments.
Gel electrophoresis animation
Step 3: The DNA fragments are transferred to a nylon sheet by placing the sheet on the gel and soaking them overnight.
Step 4: A radioactive material is added which combines with the DNA fragments to produce a fluorescent image.
A photographic copy of the DNA bands is then made.
In a standard DNA fingerprint, about a dozen sites are analyzed, with each site having many possible alleles.
The chance that two patterns will match is incredibly small: 1 in 30 million (except for identical twins).
Examine the DNA fingerprints at the right. A man with blood on his shirt was arrested for murder. He claimed that he had cut himself, and the blood was his. Is he lying or telling the truth?
DNA detective animation
HGP fingerprinting page
Forensic science (solving crimes)
A murder victim is found. The forensics team retrieved a blood sample from the crime scene. They prepared DNA fingerprints of the blood sample, the victim and a suspect as follows:
Blood sample from crime scene
In 1994, Royal Canadian Mounted Police detectives successfully tested hairs from a cat known as Snowball, and used the test to link a man to the murder of his wife, thus marking for the first time in forensic history the use of non-human DNA to identify a criminal.
Yup, he did it.
DNA fingerprints can be used to determine whether a particular person is the father (paternity) or mother (maternity)of a child.
This information can be used in
In the 1920s, Anna Anderson claimed that she was Princess Anastasia Romanov of Russia. In the 1980s after her death, samples of her tissue that had been stored at a Charlottesville, Virginia hospital following a medical procedure were tested using DNA fingerprinting and showed that she bore no relation to the Romanovs.
Examine each set of DNA fingerprints above.
Determine if each alleged father is, in fact, the father of the child. If the child and man share the same allele, the man is the father.
personal identification in the armed services(instead of dogtags, dental records or blood types)
identifying human remains.For example, many of the victims of the 9/11 terrorist attack were identified by DNA fingerprinting.
matching organ donorsto people needing an organ replacement.
diagnosing inherited disordersin prenatal and newborn babies.
research on genetic disorders.
as well as…
studying populations of wild animals
Whose hair is it?
Other forensics problems