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Deoxyribose nucleic acid, a.k.a. DNA, is the double-stranded polymer that contains the genetic instructions for life as we know it. Since scientists discovered DNA in 1953, there has been an upsurge in the amount of research and innovation people can do with DNA. Examples include cloning, recombinant DNA technology, DNA fingerprinting, and in agricultural biotechnology. Studying DNA so heavily across many organisms is why society can create new genetic processes to help with current biological problems. Having this whole database on DNA now will also carve the path for future scientific innovations in genetics and beyond. Going back to the technology involved with DNA, one such process is DNA fingerprinting. This blog will closely examine how DNA fingerprinting works and its societal benefits.
DNA fingerprinting, also referred to as DNA profiling and DNA typing, is the technique that lets one identify individuals solely based on their DNA sequence. Since everyone's DNA sequence is unique, it is easy to use DNA fingerprinting in many areas. For instance, police may identify a suspect by finding and matching their thumbprints from things they've touched. We've all seen this happen in movies. Scientists may also use DNA fingerprinting to track DNA back generations in human ancestry and find family trees. DNA fingerprinting can also be utilized in medical areas for research among people or further studies. The process benefits hospitals where doctors can make patients their DNA profiles. If someone has a disease, medical professionals can study their DNA to see where the problem originated. The list of the uses of DNA fingerprinting can go on and on, but what lies in the actual process? How do scientists do DNA fingerprinting?
For starters, there must be a DNA sample in any case with DNA fingerprinting. There are many ways to get DNA from someone else, such as picking a hair off their head, taking their blood, or swabbing the inside of the cheek. These samples are usually sent to a lab where doctors can study them and closely examine the DNA inside each piece. Scientists must chemically extract the DNA from the selection so that the DNA doesn't get ruined. The next part of the DNA fingerprinting process is where the DNA has to be cut into many pieces. Restriction enzymes do this job by cleaving DNA into fragments where all the cuts made are at specific nucleotide sequences. After cutting the DNA up, the overall DNA fingerprinting process can be split into more processes to comprehensively analyze the person's DNA. These methods include gel electrophoresis and the polymerase chain reaction (PCR).
Gel electrophoresis is how DNA can be separated using electrical fields and a gel pore. The gel pore will be negatively and positively charged on both sides from the electrical field to ensure that the DNA is divided according to size. It's good to remember that DNA is a negatively charged unit. The DNA will be run through the gel pore with the help of an electrical current. Since one end of the pore is a positive set, the DNA will try to go to the other side since it's negative (opposites attract). This is where the split of the DNA is significant because it's based on either the small or large sizes of the DNA.
Depending on the size of the DNA, that will measure how fast it will go through the gel pore. If there's small DNA, it will go more quickly to the other side of the pore than the longer DNA, which will go slower. Once the electrical current has been turned off, one can see that the original DNA taken in is now a split, with the shorter DNA on one end and the larger DNA on the other. Since DNA comprises base pairs, one would see several bands of DNA, small and big, after gel electrophoresis. After removing the new DNA from the gel, scientists usually used radioactivity and other techniques to make the final DNA fingerprint for the person. While gel electrophoresis is one process one can use in DNA fingerprinting, it can sometimes turn out wrong because of external factors like incorrect sample preparation or problems with the gel. All in all, gel electrophoresis in DNA fingerprinting is a standard process, but it may not be the best.
A second system that can be used to study the DNA in DNA fingerprinting is the polymerase chain reaction or PCR. In PCR, the DNA taken from the person is amplified to have numerous copies of itself. Doing this will make it easier for people to study the given DNA sample without looking for the sequence again in the person's genome.
There are three steps in PCR: denaturation, annealing, and extension. In denaturation, the two strands of DNA are separated by heating the DNA. Next, in annealing, short pieces of DNA called primers will attach to their complementary sequence in the DNA strand. There will often be a lot of primers added just so in case the original DNA doesn't stick back together. Finally, in the last step of PCR or extension, the DNA strand is heated again to allow the primers to stick with their sequence. One crucial enzyme comes into play here, and that is DNA polymerase. DNA polymerase will go to where the primers are and start building a new DNA strand. They will add the nucleotides that are needed. The result is a complementary strand of unique DNA. From the original DNA we had, we now have two. The PCR process will repeat over and over again to make more DNA. By replicating DNA like this, PCR has become a revolutionary process in genetics, and it can be combined with other methods like gel electrophoresis to output a better study of DNA from anywhere.
All the individual DNA sequence variations gotten are called polymorphisms. Single nucleotide polymorphisms (SNPs) and short tandem repeats (STRs) are the two polymorphisms. A DNA profile created using these polymorphic areas contains many numbers or graphic representations showing the various alleles at each locus. The resulting profile works as an individual's genetic "fingerprint," accurately and explicitly capturing their genetic identity. The more studies and tests one does on the DNA profile, the more accurately it can be matched to people.
Now that we've talked about the science behind DNA fingerprinting, we should also go over the uses of the process in today's world. Scientists often use DNA fingerprinting in forensics to aid in criminal investigations. They extract DNA from a crime scene and match it to suspects. Another area people utilize DNA fingerprinting is ancestry. It can be used to track relatives or find parents of children based on the similarities of the DNA fingerprints. Finally, DNA fingerprinting can be studied more in medical areas to stop diseases from running in families or to make more DNA profiles in a database. People can use DNA fingerprints in research as data to produce family trees or anything else.
DNA fingerprinting and making DNA profiles is still a relatively new science that is revolutionizing how we can study genetics and has more potential to be applied in more areas of life. The ability of DNA fingerprinting to reliably identify persons, improve medical research and diagnosis, and offer insights into human ancestry will make it a game-changer. As it develops and new applications emerge, this technology has the potential to unleash advances and discoveries that will change the course of scientific innovation in the future.
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REFERENCES/SOURCES
https://www.yourgenome.org/facts/what-is-a-dna-fingerprint/
https://www.webmd.com/a-to-z-guides/dna-fingerprinting-overview
https://nebula.org/blog/what-is-dna-fingerprinting/
https://www.geeksforgeeks.org/dna-fingerprinting/
https://www.thoughtco.com/what-is-dna-fingerprinting-and-how-is-it-used-375554
Image Credits
First image: Image by Gerd Altmann from Pixabay
Second image: iStock
Third image: Genome Research Limited
Fourth image: Iowa State University Biotechnology Outreach Education Center