DNA Identification,How It Works

DNA testing is the best method for recognizing human remains, particularly in mass casualty situations where it can be tough to identify bodies otherwise.

Following the crash of the Air India Boeing 787 Dreamliner in Ahmedabad, officials are utilizing DNA analysis to help identify the remains of the victims. They’ve already gathered DNA samples from the families of the victims, and a few of the remains have been identified.

Aside from identical twins, each individual has their own unique DNA found in almost every cell of their body. DNA identification is considered the best method for recognizing human remains, particularly in situations like mass fatalities where identifying bodies can be challenging. So, how does this process actually work?

Gathering And Storing Samples

Once a person passes away, their DNA starts to break down. As time goes on, this breakdown can complicate or even prevent the analysis of the DNA. How much the DNA degrades varies based on the type of tissue it’s taken from and the environment in which the body is stored, along with other factors.

DNA does way better in cold and dry conditions compared to hot and humid ones. That’s why it’s super important to collect samples as quickly as possible, and once you have them, store them in a cool and dry place. Ideally, they should be frozen at minus 20 degrees Celsius, or if you’re dealing with soft tissues like skin and muscles, you can keep them in 95% ethanol.

Soft tissue DNA breaks down a lot quicker than DNA from hard tissues like bones and teeth. This happens because the cells in hard tissues are mostly shielded from the effects of decay and decomposition. That’s why forensic investigators typically go for DNA from hard tissues.

After plane crashes, gathering tissue samples from the wreckage usually takes a few weeks. But it really depends on how big the tragedy is.

Once the samples are gathered, the next move is to extract DNA from them. Following this, based on the quality of the extracted DNA, researchers may select from various analytical methods.

Short Tandem Repeat (STR) Analysis

This method looks at short tandem repeats, which are basically short sequences of DNA that repeat. STRs are crucial for DNA identification since they differ significantly among individuals. According to a report from the International Committee of the Red Cross (ICRC), “After analysing 15 or more of these hyper-variable regions of DNA… the resulting profile can be used to ascertain family relationships with a high degree of confidence”.

It’s important to note that STRs are usually found in nuclear DNA, which is located within the nucleus of a cell. So, for STR analysis to be effective, the nuclear DNA extracted from the sample must be intact and not degraded.

Mito Chondrial DNA (mtDNA) Analysis:

This technique comes into play when nuclear DNA is either damaged or not accessible. Mitochondrial DNA resides in the cell’s energy-generating structures called mitochondria. Since mtDNA exists in several copies within the cell, it’s simpler to extract from human remains that aren’t in great condition.

This helps with identification since mtDNA is inherited from the mother, remaining the same for all her kids. So, samples taken from individual’s remains can be compared with reference samples from their mom, maternal grandmother, siblings, maternal aunts or uncles, and even distant relatives, as long as they come from the maternal lineage.

Y Chromosome Analysis

Humans possess two kinds of sex chromosomes, X and Y. Generally, biological males have one X and one Y chromosome, while biological females usually have two X chromosomes.

In this approach, a panel of STR markers on Y chromosomes, inherited from father to son, is analyzed to connect the victim’s remains with their male family members.

Analyzing Single Nucleotide Poly Morphisms (SNPs)

This method is usually applied when the DNA being examined is significantly degraded. An SNP represents a change in the DNA sequence where one base A, C, G, or T at a certain spot varies between individuals.Since SNPs are distinct for each person, they can be utilized for identification by comparing them to reference samples collected from, for example, the victim’s personal items like a toothbrush or hairbrush.This approach isn’t as effective as STR analysis.