The 20th century opened the floodgates for advancement across the board, from technology to medicine—even more efficient and effective crime-solving techniques. One of the most effective strategies humans have used to catch criminals is known as the DNA fingerprint. DNA fingerprinting is a method that is used to identify an individual from a sample of DNA. This technique of identifying patterns in DNA dates back to 1984 when it was invented by Professor Sir Alec Jeffreys. This complex technique has many uses, including physically connecting a piece of evidence to a suspect or ruling out suspects in a crime, identifying a dead body that’s too old or damaged to be recognized, and showing who one’s biological relatives are.
The procedure for DNA fingerprinting tests is a lengthy, but highly accurate process, starting with the first step of extracting the DNA from a sample of human material, typically blood.
Then, restriction enzymes are used to cut the DNA, resulting in multiple pieces of DNA with a variety of lengths.
These pieces are then separated by size through a process called gel electrophoresis. In gel electrophoresis, the DNA is put through one end of a porous gel. An electric current is applied which pulls the DNA, which has a negative charge, through the gel. The shorter pieces of DNA move through the gel easiest and fastest, in contrast to the longer pieces, which take longer and therefore move slower than the smaller pieces of DNA. When the electric current is switched off, the DNA pieces are now separated by size (the longest pieces were the closest to the gel, and the smallest ones were the furthest away).
Once the DNA has been sorted in accordance with size, the pieces of DNA are removed from the gel and transferred onto a piece of nylon, where they are taken apart to produce single strands of DNA.
Next, the nylon material is incubated with radioactive probes. The probes only attach to the pieces of DNA that they are complementary to, such as A to T and G to C.
Then, the nylon is exposed to an X-ray film. When exposed to radioactivity, a pattern of over 30 dark bands forms. This pattern is the DNA fingerprint. When wanting to compare two DNA fingerprints, the different DNA samples are run next to each other on the same electrophoresis gel.
DNA technology plays a crucial role in the fairness of the criminal justice system. DNA fingerprinting has impacted the way criminals are caught because of its high accuracy. It has proved itself to be one of the most successful and effective approaches to criminal justice. The DNA left at the crime scene can be matched to the DNA of potential suspects, so that a criminal in a particular situation can be caught. There have been many cases in which DNA testing has played a significant role in catching the individual behind the crime, such as in the 1973 murder of Linda O’Keefe. For many years, her death had remained a mystery, until February 2019, when her killer, James Neal, was found after forensic DNA testing was conducted and an online genealogy website revealed a DNA match with the evidence that was left at the crime scene.
As we continue to make strides in a range of fields, we have every reason to be excited about the number of unresolved problems that modern advancements like DNA fingerprinting can tackle.
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