CSI:Norwich - Part 2

Hi everyone!

It's time to finish off my summary of our recent CSI:Norwich event which took place during the Norwich Science Festival. Don't forget to check out the previous post for an introduction to the event and a brief description of the first two activity stalls (Fingerprinting and Pen Chromatography).

Activity #3: Blood Groups

Stall number 3 focused on blood testing and how antigens found on the surface of red blood cells relate to the four main blood groups: ABAB and O. With respect to the crime scene, blood recovered from the victim's fingernails was found to be blood type A, so visitors could eliminate a suspect if they didn't have this blood type. To illustrate how it is possible to distinguish between different blood samples, we asked visitors to perform a simple, representative experiment using 'blood' (actually just water with lots and lots of food colouring!) from each of the suspects:

First, a drop of calcium lactate solution (representing an antibody that binds specifically to blood type A antigens) was placed in a Petri dish and then a drop of the suspect's blood was added on top. Some of the blood samples contained alginate (these were classified as blood group A) and immediately coagulated when mixed with calcium lactate. The other samples (not classified as blood group A) did not contain alginate and stayed as a runny liquid upon mixing. It was therefore possible to differentiate between blood samples because they had different physical appearances after mixing (and only those that coagulated could be assigned to blood group A). N.B. Although this wasn't an actual reaction that would be performed in a forensics lab, it allowed for a great discussion of antibody 'lock and key' mechanisms!

Activity #4: DNA

The fourth activity station involved a paper-based assessment of DNA (which stands for deoxyribonucleic acid, a biological molecule that carries genetic information) taken from the suspects to work out whether it matched the DNA found on the victim's body. Unfortunately there wasn't enough time for visitors to carry out an experimental DNA extraction so we printed reels of paper with long letter sequences corresponding to the building blocks of DNA called nucleotides (more specifically: adenine [A], cytosine [C], guanine [G] and thymine [T] written in sets of three). The visitors then had to compare the suspect DNA sequence to the crime scene DNA sequence and eliminate a suspect if there wasn't an exact match.

Activity #5: Clothes Fibres

The final stall at CSI:Norwich gave visitors the chance to analyse the physical properties of different clothes fibres and then determine whether those taken from the suspect's clothing were the same as those discovered at the crime scene. The fabric samples included knitted wool, woven cotton, satin polyester and nylon lace - all of which differ in how smooth/rough and stretchy/firm they are. In addition to how they felt, visitors could take a closer look at the weave of the thread using a digital microscope, making it possible to separate seemingly identical pieces of black fabric. For example, the cotton consisted of a regular over-under weave with a criss-cross pattern whereas the satin threads were tightly packed with very little crossover!

Well that brings me to the end of this blog post. I hope that everyone who visited CSI:Norwich had a fantastic time analysing our crime scene and performing science experiments. BSA Norwich will be back soon with even more exciting events! Before I go, I want to thank all of our enthusiastic and energetic volunteers - the day would not have been possible, or nearly as enjoyable, without you! 

As always, if you have any thoughts or feedback regarding events, social media activity and blog posts from BSA Norwich then we'd love to hear from you! Also, please get in contact if you'd like to volunteer. :)