February should be called DNA Month - Strawberry DNA Extracting
DNA is the building blocks to all life
Deoxyribonucleic-Acid, or DNA for short, is the genetic material that forms the basis of all life. Without DNA, you would basically be a rock (i.e. rocks are not living and therefore don't have DNA). Another way to think of DNA is to compare it to a building's blueprint; it is the instruction manual for constructing life.
DNA lives in the nucleolus of every living cell. It takes the form of a double helix structure, usually depicted in a counter-clockwise rotation (upwards). Some might refer to its unwound shape as a ladder, with two sugar phosphate 'sides' and rungs made of 4 nucleotide bases joined 1:1: Adenine, Thymine, Cytosine, Guanine. Unique is also the fact that if you look at the 'rungs' of DNA, Adenine will only pair with Thymine, and Cytosine will only pair with Guanine. If you really want to get minuet, the whole of DNA is purposefully designed based upon the use of the 5 base atoms: oxygen, carbon, hydrogen, phosphorus, and nitrogen. All of the instructions of life as we know it, are based on these 5 compounds!
Random or not, DNA is a unique component of life and well worth some admiration from us all. Without it, we would cease to be. We get all of our inherited genes, characteristics, looks, structures, etc... based off of our DNA. And despite what you might have heard, WE each have our OWN UNIQUE and INDIVIDUALIZED DNA different from every other living thing on the planet (when you look at the whole strand in entirety!).
Forensic Science, you will find yourself coming to appreciate DNA even deeper. Because DNA is so unique to the individual, traces of cells left at crime scenes can be collected, DNA extracted, and 'mapped' at unique points of the genetic code to connect an unknown cell to collected samples of known source cells. This can lead to arresting and bringing to justice the bad guys, or acquitting a suspect who had nothing to do with the crime.
If you haven't guessed yet, I'm pretty stoked to be sharing my thoughts on DNA!
Scientific details and descriptions aside, I'm now just as (OK MORE) excited to share with you an experiment you can do at home to actually SEE DNA, and have some fun while doing it!
DNA Extraction Process from a Strawberry
You can actually extract DNA from any living cell, but strawberries are fun because you can really see the DNA appear well.
What You Will Need:
- 3 Red strawberries - tops removed
- 3 3/4 Cups ice cold water - no ice
- 1 Never opened Ziploc quart bag
- 1 Measuring cup that measures in ml (up to 50ml)
- 50ml Dish soap
- 2 tea. Salt
- Strainer
- 2 Glass mixing bowls
- Graduated cylinder OR a plastic see through cup works too!
- 1 Popsicle stick
- Pinch of meat tenderizer
- 30ml of freezer cold isopropyl alcohol (90-99% works best)
- 1 Toothpick
The Steps:
- Place isopropyl alcohol into the freezer to begin chilling.
- In one of your glass mixing bowls, combine water, dish soap, and salt. Mix thoroughly until salt is dissolved, but don't cause soap bubbles! Set aside for now.
- Place your 3 strawberries inside the Ziploc bag. Seal air tight and mash, careful not to break the bag. Mash for about 3 mins or until berries are flat and juicy.
- Carefully open the Ziploc bag and pour 30ml of your water-soap-salt mixture into the bag. Remove air and seal bag. Mix the strawberry mixture again for about 1 min.
- Place your strainer over your second glass bowl. Pour strawberry mixture into strainer to separate skins/fruit from the juice mix. Catch as much juice as you can and dispose of berry solids.
- Pour juice into graduated cylinder (1/3 full) OR into your clear plastic cup.
- Allow juice to rest 10 mins.
- After 10 (or more) mins, sprinkle a pinch of meat tenderizer into your juice; you can use an actual pinch or a popsicle stick end can be used to add it in.
- Using the popsicle stick, GENTLY stir in the meat tenderizer until dissolved - BE CAREFUL as you can break down the DNA by stirring too hard during this step!
- Take your freezer cold alcohol and measure out 30ml into a clean measuring cup.
- Taking the juice cup/cylinder and alcohol, gently tip the juice holder diagonally and gently pour the alcohol down the side of the juice container so it sits gently on top of the juice mix (it will naturally want to sit on top because it is less dense than the juice below it, but be careful anyways to do this step slowly and gently!)
- Watch the area where the juice and alcohol meet. You should start to see a cloudy, stringy substance forming. Welcome to your strawberry's DNA!
The Science:
How'd we do it? Well you should know that DNA is stuck in the nucleolus of the cell AND that DNA doesn't just 'hang out' in there, but is held in tight shapes called chromosomes which form as the DNA circles around proteins called histones. So in order to see DNA with the naked eye, we have to do a couple different steps in the proper order.
Water-Soap-Salt: Water is polar (charged), DNA is polar; so first we need to neutralize (no charge) our water with salt to keep the DNA from sticking to it (and us not being able to see it).
DNA is protected by at least 2 membranes: Cell Membrane and Nucleolus Membrane. These have to be broken down so the DNA can be reached and released from the cell. Soap is our solution to this as soap molecules attach to membranous molecules to break them apart and make for easy cleaning.
This gets us to the DNA, but remember, DNA is wrapped up in chromosomes, tightly around histones, so we need a way to dissolve the histone proteins without hurting the DNA. Here entered the enzymes (meat tenderizer) to break down the histone proteins, and allow our strawberry DNA to begin unraveling. Did you know if we completely unraveled 1 DNA strand it would be over 8 feet in length?!?!
Now our DNA is free! How do we see it? Cold alcohol. Added slowly to the juice mixture, it sits on top (less dense) and at the apex meeting of juice and alcohol, little white clouds/strings of DNA start to be drawn up into the alcohol layer and 'appear' before our eyes! DNA won't dissolve in alcohol and instead begins clumping together even as it strings out - allowing us to see the DNA.
Take it Further:
- Experiment with another source of DNA. Which sources are giving you more DNA?
- Use different soaps and detergents, powered vs. liquid, shampoo or body scrub.
- Leave out or swap steps. What happens and can you explain why?
- Do ONLY living organisms have DNA? Try extracting DNA from a source you call non-living.
