How Is a DNA Fingerprint Made


DNA fingerprinting is the method done to identify an individual using a sample of DNA and by checking at the unique patterns present in their DNA. Each person has a unique pattern of DNA fingerprint and does not share it with any individual in the world except if they have an identical twin.

DNA fingerprinting is made by collecting any DNA sample from a subject and undergo a process where the DNA sample is isolated. Once isolated, the DNA sample will undergo a process called Gel Electrophoresis to separate it into DNA fragments which will then be sieved from the gel using a nylon membrane. The nylon membrane will then be exposed to radioactivity which allows it to turn into a pattern of unique dark bands which are also known as DNA fingerprint.

What is DNA fingerprinting?

DNA fingerprinting is also known as DNA typing, DNA profiling, or genetic fingerprinting. This is a molecular genetic method which allows the identification of an individual by using DNA samples such as blood, semen, hair or any other biological samples because each individual has unique patterns present in their DNA.

How is DNA Fingerprinting done?

DNA fingerprinting for humans use DNA samples from the subjects being tested, such as blood samples or swabbing of tissue from inside the mouth. The swab sampling method is usually chosen because it is less invasive, making it safe for even younger subjects. Although there are possible issues that may arise during the process, DNA samples need to be stored quickly. If the DNA sample is not stored properly, there is a possibility that bacteria can invade the cells containing DNA. Cells are not visible, and there is a possibility that the DNA sample is not present on the swab samples that are given.

When the DNA sample is received, it is then tested to check for the following:

  1. Establish a relationship between two individuals or subjects, for example, a small child and possible parent.
  2. In medical processes, it can be used to check if the donor and recipient have a good genetic match, for those donating bone marrow or any organ.
  3. Help investigators if the DNA samples found in the crime scene matches a possible suspect.
  4. Identify a decomposing body that is difficult to identify using standard processes.

DNA fingerprinting is an important test done to check the genetic makeup of a person. This process has been used by courts to review the evidence, identify dead bodies, and search for possible cures for different types of diseases. DNA fingerprinting has been used in history for tracking down relatives and family members. DNA fingerprinting is a test that can be done to check the genetic makeup of an individual, and it can also check the similarities and dissimilarities from the DNA present in different individuals.

DNA fingerprinting is a tool used by forensic investigators. The DNA fingerprint of an individual is not alterable. A person or an individual has a unique DNA fingerprint, and it used to make identification of body remains of a victim, and it will also connect them to any of the suspects in custody. DNA fingerprinting can be a tool that connects different incidents that occur in different places in the world.

When is the DNA fingerprinting first developed?

Professor Alec Jeffreys is a British Scientist from the University of Leicester who developed the DNA fingerprinting in 1984. The nucleotides sequence in a DNA is similar to a person’s fingerprint, it is unique, and no individual has the same DNA fingerprint, except if he or she has an identical twin. An individual’s DNA fingerprint is the same in every cell, tissue, and organs. It is effective in identifying unknown people, researching different populations, and investigating forensics.

DNA fingerprinting has been used widely because it allows the proper identification of an individual and it can be used in health care research and allows the diagnosis of genetic disorders that can be passed from parents to their children. Investigators use DNA fingerprinting to catch suspects for their crimes committed, and it is also used to solve and identify paternity cases. DNA fingerprint is the unique pattern of DNA that occurs in a unique sequence. DNA fingerprinting is also known as DNA typing.

How is the DNA fingerprint produced?

  1. The DNA sample is extracted from a human subject, any DNA sample can be used, such as blood, body fluids, hair, teeth, bones, semen, and vaginal fluids, etc.

If there is a limited amount of DNA sample available for the DNA fingerprinting process, the next step can be done, which is known as Polymerase chain reaction. This process will help replicate the DNA sample; therefore, more DNA sample can be tested and researched accordingly.

First, after the DNA sample is isolated, DNA will then be tested. Restriction enzymes will be applied to the DNA sample; these are used to cut the DNA and produce different pieces of DNA with various lengths.

The different sized fragments of DNA are known as restriction fragment length polymorphisms.

The DNA fragments can be observed by doing the process called gel electrophoresis. This method separates the DNA based on the fragment samples.

The next step is to conduct a process called Gel Electrophoresis. This process uses electrical current and applies it in a mixture of porous gel which includes the samples of the DNA fragments.

The electric current pulls the negatively-charged DNA and allows the DNA strands to move in the gel and separate the DNA molecules of different sizes. The shorter fragments of DNA will move fastest and easiest while the longer fragments will travel slower than the others.

After the electric current is applied, the DNA fragments will be arranged according to their sizes. The smallest molecules will be farthest from where the original sample of the DNA was originally placed in the gel mixture.

The fragments of DNA are sieved from the gel using a nylon membrane. The nylon membrane is treated with chemicals that help break the hydrogen bonds of the DNA fragments. This process will produce single strands of DNA.

The nylon membrane will be incubated using radioactive probes. The probes are small fragments of minisatellite DNA applied with radioactive phosphorus. The probes will only attach to the fragments of the DNA that they are complementary with – this means they will only attach on the minisatellites in the genome.

The minisatellites that the probes attached to will then be checked by exposing the nylon membrane using UV light, heat or X-ray film.

When the minisatellites are exposed to radioactivity, a pattern consisting of 30 dark bands will appear in the film where the DNA is present, this pattern is also known as the DNA fingerprint. Different DNA fingerprints from different DNA samples can be cross-checked by running them side by side on the electrophoresis gel.

The probes show up on the photographic film because the DNA strands decay and give off light, and then it leaves dark spots, the dark spots are called DNA bands of a person. DNA fingerprint is consisting of the unique patterns of bands; a person’s DNA fingerprint varies from other individuals except for those who have identical twins. The technique used for this process is called Southern blotting.

DNA fingerprinting can be used which DNA sample belongs to which person, for example, there are hair strands present in a crime scene, and it can be used to pinpoint which individual it belongs to.

Parents’ fingerprints are usually similar to their children. Although not totally the same, there are instances that there are some bands that match one parent and the other bands match the other parent. The combination of the bands of the parents helps identify their child.

What are the advantages of DNA Fingerprinting?

  1. This process is affordable.
  2. It is a reliable method and helps produce correct results.
  3. It is easy and painless for the subject being tested. It is better than other invasive measures. This is safe for even young subjects. It is commonly used to test the DNA of a baby and match it with the possible father.
  4. This process can be conducted quickly and offers fast results.
  5. Any subject no matter the age can be tested without any issues or concerns that may arise.
  6. DNA fingerprinting is quite useful in different ways such as legal claims, missing person cases, paternity tests, searching for possible suspects of crimes, prenatal testing, and identification for the military.
  7. DNA fingerprinting has been used and developed since 1984, and it has been improved ever since.

What are the disadvantages of DNA Fingerprinting?

  1. The DNA sample can be ruined during the process of DNA fingerprinting; there is a possibility it can become useless and will not be valid to test for any results.
  2. The process must be done in a laboratory because it is complicated and tedious and needs to be performed by an expert.
  3. The DNA fingerprinting test needs to be run using multiple samples to get accurate results. A laboratory can run each test twice using four samples.
  4. There is a possibility that there are factors or any privacy concerns that can occur if the information is not kept secured in the laboratory. The data is only allowed to be released legally if there is a written order. If there is information that is leaked by those involved in the process, it can complicate the health care, job prospects, or insurance processes of the subject involved.
  5. The results can be difficult to interpret.

What are the common uses for DNA fingerprinting?

  1. Agriculture – DNA fingerprinting has been used in the Agriculture industry to help produce and identify genetically modified plants, and this can provide various plants that have therapeutic value and medicinal uses. This process also proves an animal’s pedigree value; an example of this are racehorses. Even plants and animals have DNA, which makes them perfect for DNA fingerprinting processes as well.
  2. Forensics – DNA fingerprinting can be used to find suspects in a crime. A lot of time, fingerprinting can exonerate innocent people that are charged with crimes. DNA fingerprinting is a process that can help identify a decomposing body that can be difficult to identify using normal processes.
  3. Medicine – DNA fingerprinting is useful in the medical industry. This process is used for identifying possible matches when performing organ or bone marrow donation. A lot of medical experts and scientists use DNA fingerprinting to design possible treatments for cancer patients. DNA fingerprinting helps ensure that a tissue sample is properly labeled with the correct patient’s name, making the process easier, preventing any mistakes, and produce accurate results.
  4. Identification – DNA fingerprinting is a process that helps identify a baby’s birth father. DNA fingerprinting has been used to establish an individual’s relationship to the deceased when it comes to cases of inheritance. This process also helps families that are separated because of different causes such as a natural disaster or war, making it easy to find small children and connect them to their birth parents.

Photo credit: ©canva.com/mj0007

Ryan Sanders

Ryan Sanders is an aspiring genetics science enthusiast. His journey started with curiosity about his roots. He keeps learning more about genetics every day.

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