7/29/2019 Bloody Bats - Fake DNA

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Bloody BatsFake DNA?

Last Thursdays class, Romie Littrel conducted a fun and enlightening workshop that utilized polymerase

chain reaction or PCR to find those in the class who have the gene that encodes for bitter taste

perception. I have always been curious about PCR because, even though I learned about it theoretically

from my community college in biology and organic chemistry, my lab experience in replicating DNA wasby using bacteria (i.e. the old way). PCR is quite fascinating in that it speeds up what usually takes

days, in to just about two hours. In those two hours, the PCR enables researchers to produce millions of

copies of a specific DNA sequence through cycles that consist of heated denaturation, annealing left and

right primers, and Taq polymerase (a thermostable DNA polymerase enzyme that synthesizes DNA

molecules from its nucleotide building blocks) synthesizing new DNA. Using PCR in class brought to

mind an application of PCR that, being a murder-mystery fanatic when I am not pounding away at my

textbooks, I encountered in the past: fabricating DNA evidence. In 2009, Israeli scientists developed a

means of fabricating blood and saliva samples containing DNA from a person other than the donor of

the blood and saliva. In addition, they even found the method of using a DNA database profile to

construct a sample of DNA to match without obtaining any tissue from the profiled person.

There are two methods to obtain fabricated DNA. The first method is the most simplistic and requires a

real, if small, sample of DNA which can be then amplified into a large quantity of DNA using whole

genome amplification. The concept of whole genome amplification, also known as WGA, arose as PCR

was adapted to replicated regions of genomes that are of biological interest. WGA is the process where

genomic DNA is copied multiple times over to produce larger amounts DNA; basically an akin process to

PCR. A sample of blood is then obtained from one person and centrifuged to remove the white blood

cells. The leftover red blood cells (RBCs) that lack genetic material are injected with another persons

DNA, thus giving the blood type of the first person along with the DNA of the second. The second

method requires access to DNA profiles, usually found in law enforcement databases. These databasescontain libraries of genomes from which the scientists can clone tiny DNA snippets represntng the

common variants at 13 spots in a persons genome. To prepare a DNA sample matching any chosen

profile, researchers mix the proper DNA snippets together (they believe that about 425 different DNA

snippets would be enough to put together every conceivable profile). All in all, even though fabricated

DNA has the potential to lead to faux evidence and is a potential invasion of personal privacy to others,

it is an extraordinary use of PCR and makes for a very twisted plot in a thriller.