Intended Readers: This Instructable applies to all potential readers. However, a basic understanding of cellular anatomy may be helpful.
- Deoxyribose nucleic acid (DNA): The genetic material that makes up all living things
- Nucleotide: Base pairs found within each double strand of DNA
- Nucleus: The location of genetic material within a cell
- Chromosomes: Compacted DNA found within the nucleus of a cell
- Phospholipid bilayer: Most of the outer layer of the cell that consists of hydrophobic and hydrophilic molecules
- Hydrophilic: Water loving molecules
- Hydrophobic: Water fearing molecules
- Extracellular Membrane: The outermost layer of the cell
- Lysing: Breakdown of a cell
What You Will Need:
- Cheek cell DNA
- 2 small clear plastic cups
- 1 small bottle of water
- 2 tbsp salt
- Dish soap
- 50 mL isopropyl alcohol
- 2 drops of food coloring
- 1 Tooth Pick
Deoxyribose nucleic acid, or DNA is the genetic material necessary for replication in all living things. DNA is double stranded and made up of four base pairs known as nucleotides. These include thymine, adenine, guanine, and cytosine. Each nucleotide is paired up with a different nucleotide on the partnering strand of DNA. There are trillions of these strands within all living species.
Due to the amount of genetic material our bodies must contain, DNA is compacted into what are known as chromosomes. This genetic material is housed within the nucleus, a microscopic organelle found inside of all animal and plant cells.There are 23 pairs or 46 individual chromosomes within each human nucleus.
During cellular replication, these chromosomes will unwind. This allows the double-stranded DNA to "unzip" the partnering nucleotide base pairs. There are now two separate single strands of DNA ready to be copied. After each individual strand has been copied, the two original cells will recombine. The two copied strands will then transition into the replicated cells.
While inside the nucleus of the cell, DNA is impossible to see without the use of a microscope. However, through a process known as lysing, the phospholipid bilayer, which makes up most of the outer surface of the cell, can be broken down. This allows for the DNA strands to be released. The phospholipid bilayer is made up of two different molecules, hydrophilic (water loving), and hydrophobic (water fearing). These two compounds will form long strands that join together and will stretch the expanse of the extracellular membrane, or the entire outer surface of the cell. The extracellular membrane is made up of the phospholipid bilayer, proteins, and carbohydrates.
In this experiment, we will use common household kitchen items to break down the phospholipid bilayer, and extracellular membrane. The ingredient used in this experiment to break down the hydrophilic and hydrophobic molecules will be dish soap. Dish soap contains chemical properties that can cause the bonds between the two molecules to break down. Eight different ingredients will be used in order to make the DNA viewable to the naked eye.
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Step 1: Mix Water and Salt
See Figure 2
1. Pour bottled water into the clear plastic cup until three-quarters of the way full.
2. Transfer 2 tbsp of salt into the mixture and stir until dissolved.
This purpose of this process is to allow the cheek cell DNA to clump together after the cells have been lysed. Once the extracellular membrane has been broken down, the DNA will then be free to transition out of the cell. From there, with the assistance of the salt water, it will form visual clumps and strands of genetic material.
Step 2: Gargle Salt Water Solution
See Figure 3
1. Pour 3-4 tbsp of the salt water solution into the remaining cup
2. Gargle this solution for 30-60 seconds, but do not swallow it
Make sure to swish the solution from cheek to cheek while gargling. This will ensure that an effective amount of cheek cell DNA is mixed in with the salt water.
3. After gargling, spit the solution back into the second cup.
Your cheek cells have now been intermixed with the solution. However, since the extracellular membrane has still not been lysed using dish soap, this step will have no effect on the DNAs' overall visual appearance.
Step 3: Pour in Dish Soap
See Figure 4
1. Pour 2-3 drops of common dish soap into the solution
- This step will begin the process of breaking down the extracellular membrane. The dish soap will disrupt the bonds between the hydrophilic and hydrophobic molecules in order to denature (deform) the cells membrane. Once the dish soap has pulled apart these bonds, DNA will be free to leave the cell.
2. Stir the solution gently with a toothpick until mixed
- This is the step that will lyse, or break down the extracellular membrane and allow the DNA strands to flow outward. Mixing the dish soap into the solution ensures that all of the extracellular membranes break down.
Step 4: Pour in Alcohol
See Figure 5
1. Pour 3-4 tbsps of isopropyl alcohol into the solution
- Do not let the alcohol mix with the salt water/cheek cell solution underneath it. In order to prevent this from occurring, pour the alcohol down the interior side of the cup. Afterward, a small layer of alcohol should remain separated from the solution.
- The purpose of the alcohol in this step is to separate the DNA from the other components of the solution. Extracted DNA should begin to form in between the layer of salt water, and the layer of alcohol.
Step 5: Add Food Coloring
See Figure 6
1. Pour in 2-3 drops of food coloring.
- This can be any color. The purpose of the food coloring is to allow the DNA to become more visible. Often times, the clumped DNA can be difficult to see inside of the plastic cup. The solution is hazy due to all of the different ingredients. Saliva can also be mistaken for DNA without the use of a proper contrast.
Step 6: Final Step
See Figure 7
1. Wait 3-4 minutes
- Small strands and clumps should begin to form inside of the solution. Take the toothpick and gently fish out one of these strands. This is the cheek cell DNA bonded together.
- Helpful Tip*- in order to extract the most amount of DNA possible, twirl the toothpick around in the solution and remove it slowly. This will allow the DNA to stick briefly to the end of the toothpick rather than fall back into the cup.
In conclusion, this Instructable demonstrated how DNA can be extracted from a cell by using common household kitchen items.
For more information on cellular functions and DNA see the following links below: