Hello, and welcome back, folks, to another episode of STEM on the Streets! If you are new here, my name is Aiza, and this is my partner CAI (crime Ai), together, we stroll through the criminal-ridden streets of STEM!
If you haven't read the previous episode, click on the button to read it!
A DNA Recap
Here is a quick recap of what DNA is and where it can be found. DNA stands for deox- doxy- dox-
(✿◡‿◡)CAI: Deoxyribonucleic acid
Ah, yes thank you CAI.
DNA stands for Deoxyribonucleic acid which is the genetic blueprint of all living things and it basically determines the traits within an organism (these traits could be physical, relating to certain diseases or disorders passed down from parental DNA and many other things). It is unique for every individual, except identical siblings, and due to its uniqueness, it can be used to determine individuals, whether it is victims or perpetrators at crime scenes.
DNA can be found in multiple bodily substances like blood, semen, urine, sweat, saliva, hair, and other bodily substances, and is even found in tears! In other ways, it is impossible to not leave DNA traces anywhere, even when the perpetrator is fully covered, DNA traces can even be left by simply breathing. Humans shed causing them to leave traces of DNA in forms such as dead cells and hair and even if the traces of DNA are very small, technology has developed so much that even fragments of DNA can be analyzed and used as evidence. So if you wanted to leave no traces of DNA at all, you’d have to be covered from head to toe and not breathe in the environment- so you can consider it impossible. Cool isn’t it?
DNA Profiling
Now that you have a quick recap of what DNA actually is, it is time to go to DNA profiling, where the magic or crime-solving starts. So once a DNA sample is collected, it is analyzed. There are specific parts of DNA, loci (like a location or address, you may say, of a gene or genetic marker) which are like points of DNA that create a DNA profile, completely one of a kind for every individual.
Once a DNA profile is created, it is compared to other profiles, such as comparing the DNA profile of some DNA found at a crime scene with the one of a suspect. However, sometimes evidence isn’t enough to produce a complete DNA profile if the DNA is degraded which means that all loci aren’t present. But sometimes, a partial profile can suffice even though it has a fewer number of loci.
Understanding Forensic DNA Some evidence may not produce a full DNA profile if the DNA is degraded, and there isn’t information present at all loci. Some DNA evidence may be too degraded for any testing. Under some circumstances, a partial profile, or a profile that includes fewer than the full number of loci detected by a particular kit, can still be compared against a suspect’s profile. A match using this method, however, will not provide the certainty that comparing two complete profiles would
A DNA Science Experiment
Have you ever wanted to see literal DNA? Like physically present in your hands? Well, if you did, you are in luck ‘cause there is a way. I remember I did this in year nine, hands down the best experiment I have ever done.
(✿◡‿◡)CAI: Yet you messed up several times because you refused to follow the instructions.
Eh, we all make mistakes, besides I was young and foolish.
(* ￣︿￣)CAI: You're still young and foolish.
You digress, back to the topic- the DNA experiment extraordinaire!
Materials:
1 ripe strawberry
A plastic ziplock bag
Measuring spoons
2 teaspoons of dish soap (10mL)
1/5 teaspoon of salt (approx 1 gram)
6.5 teaspoons of water (100 mL)
A mixing bowl
A small, clear glass and another one of any sort
A coffee filter or cheesecloth or a strainer(for filtering)
2 teaspoons of ice-cold (make sure to put it in the fridge 30-60 minutes before the experiment) 90% ethanol (10 mL)
A timer or clock
A popsicle stick (optional)
Method:
Take your mixing bowl and add 2 teaspoons of dish soap, ⅕ teaspoons of salt, and 6.5 teaspoons of water and mix properly. This is our extraction liquid.
Place the strawberries in a ziplock bag add the strawberries and crush for 2 minutes (use the timer or clock).
Once you have a strawberry pulp, transfer it to the other glass or cup and measure 2 teaspoons of the extraction liquid mix it with the strawberry pulp and mix it for 1 minute (use the clock or timer). We do this to extract the DNA from the cells. By using dish soap, which is alkaline, we can break down the cell walls which are made of phospholipids. Salt helps in clumping the DNA to make it more visible later on in the ethanol.
Filter the strawberry mixture into the clear glass.
Do you remember the 2 teaspoons of ethanol you left in the fridge? Yeah well, it is time to take it out. Now this is important, you must and I repeat must, angle the clear glass so that when you slowly pour in the ethanol, the two liquids don’t mix. We need the ethanol to be a separate layer on top of the strawberry mixture.
Leave it for 5 minutes, do not still or fiddle with it (use the clock or timer).
You should start seeing the DNA form as these clouds of strings. You can use the popsicle stick to remove the DNA strands.
The strings are the strands of DNA (The image is not mine and I'll link the website it belongs to)
Note:
If you can’t see the DNA after waiting for a good long time, try adding some more ethanol in slow and gradual amounts.
And that is it lovely folks, enjoy your experiment in whatever way you want, like I did by trying to stick some of the DNA on my squeamish brother. It was hilarious but I do not encourage that because I got a great big scolding. Anyhoo, see you next episode!
This is Aiza Jamil signing out!
I am a forensics sleuth, what's your mystery to solve?
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