DNA Profiling

  • DNA profiling, also known as DNA fingerprinting, refers to the process of examining the genetic makeup of a person. It is unique to an individual, except for identical twins.
  • This process uses the repeating sequences of DNA, which are different lengths in different individuals. It is performed on a sample of a person’s body material, such as hair, blood, or saliva.
  • DNA profiling is a powerful tool, especially in forensic science. It is used not only in solving crimes but also in paternity testing, identifying remains, and studying inherited or genetic diseases.
  • To begin DNA profiling, first, the sample is treated with chemicals that break down the cell walls, freeing the DNA within. Then, enzymes known as restriction endonucleases “cut” the DNA at specific points.
  • The DNA extracted is then copied and amplified via Polymerase Chain Reaction (PCR). This is a process of rapidly producing large quantities of specific DNA segments.
  • These amplified samples are then separated by size using a process called gel electrophoresis. The smaller fragments of DNA will move further down the gel than the larger ones, forming visible bands.
  • After electrophoresis, the DNA fragments are transferred to a nylon membrane. This process is known as Southern blotting. The transferred DNA is exposed to a radioactive labelled DNA probe that binds to a specific repeating sequence.
  • Once the probes have bound to the DNA, the nylon membrane is exposed to a film to produce an image showing the pattern of the DNA repeats. This image is referred to as a DNA profile or fingerprint, and is used for comparison.
  • Each individual’s DNA profile is unique to them (with the exception of identical twins), allowing scientists to identify individuals with high accuracy.
  • Despite its usefulness, DNA profiling has limitations. It requires a good sample of DNA, and if the sample is contaminated or degraded, the results may not be accurate. It also raises ethical issues about privacy and consent.
  • DNA profiling does not provide information about an individual’s health, appearance, or other personal traits. It simply compares genetic markers.