The human body is comprised of small set instructions that are genetically formed from the day we are born. This DNA structure is unique for each individual and it is what people can use to determine the legitimacy of their identity. And that is where DNA profiling comes along. DNA profiling is basically a process in which key genetic markers in a person’s DNA is analyzed to form a uniquely specific profile that can be obtained from any sample of bodily tissue or secretion.

One thing to note, however, is that the notion that DNA is completely different from person to person is completely false. Instead, most of our DNA is of the same structure as another which makes us all function at a base similar level. It is with a select few strands that make a person unique from one another. This specific region or strand is known as polymorphic. We inherit these variations of polymorphism directly from our parents and their parents before them. Thus, a unique set of print and genetic coding will be formed that is easily distinguishable from another, including your own siblings. In fact, even twins can have a few key differences in their genetic makeup that can be exploited for DNA profiling.

There are a variety of uses for DNA profiling but the 2 most common ones are for criminal investigation purposes and parentage tests. It does so by utilizing these key features:

  • Identifying the origin of any trace that contains DNA which could lead to discerning the criminal
  • Help reveal familial connections such as long-lost siblings and paternity tests
  • Used to distinguish disaster victims that are otherwise difficult to recognize

The Key Function of Short Tandem Repeats

DNA profiling is a long and complicated process that would require an intense amount of focus to help determine the DNA sample in question. As such one of the most common techniques being used today is through the use of researching the specific form of polymorphism called short tandem repeats.

These short tandem repeats, simply known as STRs, are specific strands of non-coding DNA that contains the same nucleotide sequence in a repeating fashion. An easier way to determine that combination is through the use of letter sequencing such as GATAGATAGATAGATAGATAGATA. These random sets of letters are known as an STR due to the repeating nucleotide sequence of GATA.

You can find this set of short tandem repeats strewn around different parts of the genetic loci inside the DNA.

DNA Profiling Basics

The DNA profile is formed from analyzing the STRs to a degree of 10 or more genetic loci. That process would involve searching through different chromosomes to receive a fully-formed genetic profile. In fact, a scientist can determine even the subject’s gender just by analyzing that specific person’s DNA structure.

How is the DNA Profile Formed Using STRs?

Retrieving the Sample

Before you can even start the profiling of the DNA, you would first need to acquire a source to test on. Fortunately, DNA can be found in pretty much the entire body. You can search for samples such as saliva, semen, hair follicles, body tissue, white blood cells, and even fingernails.

There is a near-endless supply of DNA that can be retrieved on a person as long as you are careful with your search. Sweat and saliva contain DNA through the use of epithelial cells. This is why DNA profiling is vital in solving a host of different cases that could otherwise take a long time to solve as long as the DNA evidence is not tampered with at any point.

Extract Said DNA

The nucleus of the cell is home to where the DNA is stored. As such, that is the target of every forensic scientist to break.

Certain chemicals will be required to break through the cells without damaging the DNA. Once the cells are broken all the way through, they can start isolating other components of the cell to retrieve the said sample.

Replicate the DNA Structure

DNA is hard to come by in certain situations, especially crime scenes. You cannot expect to find a myriad number of DNA evidence just lying around. That is why it is important that the evidence retrieved needs to be in mint condition.

Through the use of modern technology, however, we can use the little amount of DNA evidence retrieved and clone the specific strands of STRs using a method called polymerase chain reaction (PCR). A primer would be attached to the strain to give off a fluorescent tag to showcased the copied DNA sample to easily indicate any matching codes.

Size Up the Short Tandem Repeats

It is not just the coding of the short tandem repeats that determine the legitimacy of the DNA profile, but the size also plays a significant role. The genetic analyzer tool that DNA testing facilities utilize uses a material called gel electrophoresis to flag the fluorescent dye on each of the STR strands that match. This device is also used for gene sequencing.

Finally, Determine the Matching Traces

The amount of the repeating nucleotide sequences that are found on a certain DNA structure is determined by the overall size of the short tandem repeats. This is crucial for the scientist to determine whether or not the particular body sample is from a particular person or not.

If the 2 DNA profiles that are tested would result in a match then the likelihood of the samples to be from separate people would be drastically lower. This alone could help determine the investigations that could lead to a direct source.

It is important that scientists would only test STRs that are rated at 10 or more on genetic loci to prevent mistakes.


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