Biology Trip: Who Stole the Crown Jewels?
In May, the A level Biology students spent a day at ThinkTank in Birmingham as part of their unit 5 studies. The day was based on introducing the students to some of the techniques that are vital in forensic science and then giving them hands on experience with the equipment and methods that scientists use.
They were tasked with using the forensic science techniques of Polymerase Chain Reaction and DNA fingerprinting to help find out who stole the Crown Jewels – was it Prince Charles, Camilla, the Butler or the Queen herself?
The day started with the students preparing DNA samples from the scene of the crime and making copies of this using the Polymerase Chain Reaction. This process allowed enough copies of the genetic material from each suspect to be made so further analysis could take place. In order to carry out this procedure, the students first had to master how to accurately measure tiny volumes of liquid using a micropipette. Once they had measured their samples and loaded them into the PCR machine, we were able to recap some of the key theory relating to this process.
After lunch, the students took their newly amplified DNA samples and once again used micropipettes to load them into an electrophoresis gel. The gel, which is similar in texture to jelly, holds the samples while the process of electrophoresis takes place. Electrophoresis is the key step in separating the DNA fragments and producing the characteristic pattern of a DNA fingerprint. This stage in particular required a steady hand and a degree of manual dexterity as students had to use a very fine micro pipette to load the tiny volumes of liquid into the gel. Luckily, they had a chance to carry out some practice runs before attempting the real thing!
Once the electrophoresis had been carried out, the gel was submerged in a stain so that the DNA fragments could become visible. What followed was lots of blue hands and stained labcoats! After we rinsed the dye from the gel, the only bits that remained stained were the DNA fragments. This allowed the students to compare the genetic fingerprint from the crime scene with the DNA from the suspects. After some scrutiny, it was clear that the thief of the crown jewels was....... the butler! All of the students involved had a really enjoyable day and thanks to the techniques they carried out were able to convert theory from a textbook into personal experience. Let’s hope that this topic comes up in the final unit 5 exam!
Key Information – Polymerase Chain Reaction
The Polymerase Chain Reaction (PCR) relies on a repeating cycle of heating and cooling to make large numbers of copies of a piece of DNA. First, the DNA is heated to near boiling to separate the two strands. The temperature is then reduced while short, single stranded pieces of DNA, called primers, are added. The temperature is then raised once again to allow a second strand of DNA to form against the original template strand, thus producing another double helix identical to the original.
Key Information – Gel Electrophoresis
Gel Electrophoresis is used to separate DNA fragments according to their size. First, the DNA is loaded into small holes in a gel, then an electric current is applied to it. The DNA fragments start to move through the gel; small fragments move furthest and large fragments move the least.