DNA or deoxyribonucleic acid test is a scientific technique that identifies a person by examining his/her genetic structure. The DNA of every person in the world is different.

The plane crash that happened in Ahmedabad, Gujarat on June 12 has shaken the whole country. Air India flight AI-171 from Ahmedabad to London crashed just minutes after takeoff, killing 241 passengers. Former Gujarat Chief Minister Vijay Rupani also died in this terrible accident. The bodies of the accident victims have been burnt so badly that it is impossible to identify them through traditional methods. In such a situation, the only way left for identification is DNA test. Do you know how DNA test is done? Which part of the badly burnt bodies in the Ahmedabad plane crash will help in this work? Also, how far relatives are taken help in this investigation? 

What is a DNA test?

DNA or deoxyribonucleic acid test is a scientific technique that identifies a person by examining his/her genetic structure. The DNA of every person in the world is different and it is found in the nucleus of cells. This technique is especially useful when it is very difficult to identify the bodies. The bodies in the Ahmedabad plane crash have been severely burnt, due to which DNA test is the main means of identification. 

How is DNA test done? 

DNA testing is a difficult but systematic process. It is conducted under several stages. 

• Sample Collection: Samples are first taken for DNA test. After the Ahmedabad plane crash, the Gujarat government has made arrangements to keep DNA samples in BJ Medical College. Samples of bones, teeth, or tissues will be taken from the bodies of the deceased. These will be matched with the blood or saliva samples of their relatives such as parents, children, or siblings. 
• How are samples taken from dead bodies? To extract DNA from badly burnt bodies, samples of bones like femur, humerus or ribs are taken. Apart from this, teeth or remaining tissues are also very useful. Actually, bones and teeth are more important because DNA is preserved in them even at high temperatures. 
• Samples from relatives: Blood, saliva, or cheek cells (buccal swab) are then taken from relatives. These samples are used to match the DNA of the deceased. 

Cleaning and preparation of samples

Extracting DNA from burnt bodies is extremely difficult because high temperatures and chemicals can destroy DNA. In such a situation, the sample is first cleaned to remove external contaminants such as debris or microorganisms. For this, the sample is washed with tap water and 100% ethanol. Sterile instruments are used to grind bones and teeth into powder. 

How is DNA extracted from bones?

Organic extraction process is used to extract DNA. Under this, DNA is separated by putting the sample in a chemical solution. In the Ahmedabad accident, the bodies were affected by the fire of 1.25 lakh liters of fuel. In such a situation, the quality of DNA may be affected. However, new techniques are successful in extracting DNA from burnt remains.

How much DNA is needed for testing? 

The quantity and quality of the extracted DNA is checked through real-time PCR (polymerase chain reaction). In such a situation, first of all it is ensured whether the DNA is sufficient for testing or not.

How is DNA profiling done?

In DNA profiling, short tandem repeats (STR) are examined. These are parts of DNA that are different in every person. After this, a DNA profile is prepared. About 1000 DNA tests are being conducted in the Ahmedabad accident, which includes matching the samples of the deceased and their relatives.

How far back are samples sent for relatives?

The DNA profile of the deceased is matched with the samples of the relatives. For this, matching with the DNA of parents or children is considered more accurate because there is more genetic similarity between them. If the investigation is being done under an accident like the Ahmedabad plane crash, then this process of DNA testing can take several days.