DNA Fingerprinting Procedure , Advantage & Application | Biology

                                   DNA Fingerprinting

Good day, biology enthusiasts!

In this blog, we're diving into one of the most groundbreaking advancements in forensic science — DNA Fingerprinting. But before we explore its application, let’s understand what it actually means.

What is DNA Fingerprinting?

DNA Fingerprinting is a technique used to identify individuals based on their unique DNA profile. Interestingly, about 99.9% of the DNA in every human being is identical. However, it's the remaining 0.1% that makes every individual genetically unique.

This uniqueness is determined by sequences called VNTRs – Variable Number of Tandem Repeats. VNTRs are short sequences of DNA that repeat multiple times in a row, and the number of repeats varies from person to person.

Let’s take an example:

• Person A’s DNA: ATGC

• Person B’s DNA: ATTGC

The extra ‘T’ in Person B's sequence represents a variation in the VNTR, and it’s these small differences that allow scientists to distinguish between individuals.

🧪 How is a DNA Sample Collected?

To create a DNA fingerprint, a sample containing DNA (like blood, saliva, or hair) is collected from a suspect or individual. This sample is then processed and compared to DNA found at a crime scene or from another source.

This technique was pioneered by Sir Alec Jeffreys, a British geneticist, in 1984. He discovered that every individual carries a unique pattern of minisatellites — which laid the foundation of modern DNA fingerprinting.

 Procedure  -  A DNA fingerprint is the same for every cell, tissue, and organ of an organism. You can not be altered by any known treatment. This is a laboratory procedure consist of following steps -

Isolation Of DNA - The DNA  is isolated in a small amount from victims of blood cells or hair.

Cutting, Sizing and Sorting Of DNA - Restriction enzymes are used to cut the DNA at specific places. If there is a change in the cutting site then it will stop the enzyme from cutting the DNA. Thus a very small difference in the DNA of two individuals can result in the cut pieces of DNA of different sizes and in turn cause the fingerprints of the two individuals to differ.

Electrophoresis - The DNA is separated according to size by gel electrophoresis. Electrophoresis is a laboratory procedure in which DNA pieces are sorted by size. In this method, the DNA was loaded into the well and electric current is applied. The negative charge DNA move towards positive charge cathode through the gel. The small DNA fragments move faster than large DNA fragments. Now the electric current switch off and in this way, the DNA fragments are separated through electrophoresis.

Transfer Of DNA - The DNA pieces are transferred to the nylon sheet by placing agarose gel and nylon sheet next to each other overnight.

Probing - Probe is a fragment of DNA that can be radioactively labeled. The DNA fingerprinting is generated by adding a tagged probe to the nylon sheet. The probe only attaches to the pieces of DNA that are complementary.

DNA Fingerprints - Now this probe which is tagged is visualized by exposing the nylon membrane to the  X-Ray film. When developed, the resultant visible pattern is the DNA fingerprint looks like a bar code in the grocery counter.

Advantage Of DNA Fingerprinting -

• DNA fingerprints can not be altered by any method.
• Every individual has its own unique DNA fingerprints.
• DNA fingerprints can not be duplicated.
• It is a very reliable technique for the identification of an individual. 

Drawbacks Of Fingerprinting -

• The cost of testing is very expensive.
• Error in hybridization or probing will give wrong results.
• If there is contamination in the sample then results also affected. 

Application Of DNA Fingerprinting -

• Forensic Science - DNA fingerprinting is very helpful in detecting criminal cases like murder, robbery, rape, kidnapping, etc.
  
  
• Diagnosis Of Paternity and Maternity - DNA profiling can be used to identify whether the two people are related to one another. Thus is helpful for solving paternity or maternity disputes.
  
  
• Diagnosis Of Diseases -  DNA profiling is used in detecting genetic disorders caused in the body.
  
  
• Protection Of Legal Right -  DNA fingerprinting is used to legally protect new varieties of plants and animals.
  
  
• Identification Of Exchange Child - In hospitals some times baby are exchanged. DNA testing helps in the identification of real children.

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