2.2 The Genius of Sir Alec Jeffreys: Genetic Fingerprinting
It is surprising how many who have a passion for the biosciences (particularly genetics) do not recognise the significance of Sir Alec Jeffreys’ discovery of genetic fingerprinting and his intellect in uncovering what this novel genetic technology meant not solely for the world of genetics, but for the world in general.
Research at the University of Leicester
It was the late 1970’s and the British geneticist Alec Jeffreys was conducting his research on genetic variation within humans in the Department of Genetics and Genome Biology at the University of Leicester. He was particularly interested in understanding how small regions of the human genome could vary between individuals and how this variation might be used to track inheritance patterns.
Alec Jeffreys was studying minisatellites, short sequences of DNA that are repeated at various locations in the genome. The number of repeats in these minisatellite regions varied greatly between individuals, making them highly variable or polymorphic.
It was on the morning of September 10, 1984 that the Eureka moment occurred; whilst working with DNA samples from various individuals, Jeffreys noticed that when he used a specific probe to target the minisatellites, it revealed distinct and unique patterns of bands for each individual. The patterns resembled the unique barcodes used in fingerprinting, hence the term DNA fingerprinting was coined.
Protocol for DNA Fingerprinting
- Sample Collection: A biological sample (blood, hair, skin, or semen) is collected from an individual.
- DNA Extraction: DNA is extracted from the sample.
- Restriction EnzymeA biological catalyst that speeds up chemical reactions in cells. Digestion: The DNA is cut into fragments using restriction enzymes, which recognize and cut the DNA at specific sequences.
- Gel Electrophoresis: The DNA fragments are then separated by size using gel electrophoresis, creating a smear of DNA fragments.
- Southern Blotting: The fragments are transferred to a membrane via Southern blotting, and radioactive or fluorescent probes specific to minisatellite regions are used to bind to the DNA.
- Autoradiography: The resulting image reveals a unique pattern of bands—much like a barcode—unique to each individual. This is the individual’s genetic fingerprint.
Significance of the Discovery at the Time
Alec Jeffreys’ discovery came at a time when DNA technology was in its infancy. The ability to uniquely identify individuals based on their DNA was revolutionary. Before this, human identification largely relied on less accurate methods such as blood typing or fingerprints, neither of which could provide the level of specificity that DNA could.
Key Early Applications
Immigration Case (1985): The first real-world application of DNA fingerprinting was in an immigration case. A boy in the UK was at riskThe chance that a decision could lead to loss, failure, or negative consequences. of being deported because authorities doubted his familial ties to his mother. Jeffreys’ DNA fingerprinting technique proved that the boy was indeed the biological son of the woman, allowing him to remain in the country.
Colin Pitchfork Case (1986): This was the first time DNA fingerprinting was used to solve a criminal case. Two young girls were murdered in Leicestershire, and DNA from the crime scenes was compared to DNA from local men. Colin Pitchfork was eventually convicted after his DNA matched the crime scene evidence. This was a landmark case, showing that DNA could be used to solve crimes and exonerate the innocent.
Since its discovery, DNA fingerprinting has evolved significantly and is now used in a wide variety of fields. Here’s why it remains so important today:
Forensic Science / Criminology: DNA profiling is one of the most powerful tools in modern criminal investigations. It is used to identify suspects, exonerate the innocent, and even solve cold cases years or decades later. Moreover it has become an important tool within cases which require post-conviction DNA testing. Many people who were wrongly convicted have been exonerated through post-conviction DNA testing, reshaping the justice system.
Paternity and Family Testing: DNA fingerprinting is commonly used in paternity testing and to resolve disputes about biological parentage. It’s also used in adoption and immigration cases to prove familial relationships.