But each cell is surrounded by a sack the cell membrane. DNA is found inside a second sack the nucleus within each cell. Both soap and grease molecules organize themselves in bubbles spheres with their heads outside to face the water and their tails inside to hide from the water.
When soap comes close to grease, their similar structures cause them to combine, forming a greasy soapy ball. A cell's membranes have two layers of lipid fat molecules with proteins going through them. In this experiment, meat tenderizer acts as an enzyme to cut proteins just like a pair of scissors. Look closely. Your DNA may be lingering between the two layers of alcohol and pea soup.
Try to help the DNA rise to the top, alcohol layer. Dip a wooden stick into the pea soup and slowly pull upward into the alcohol layer. Also, look very closely at the alcohol layer for tiny bubbles. Allow more time for each step to complete.
Make sure to let the detergent sit for at least five minutes. If the cell and nuclear membranes are still intact, the DNA will be stuck in the bottom layer. Or, try letting the test tube of pea mixture and alcohol sit for minutes.
You may see more DNA precipitate into the alcohol layer over time. Keep it cold. Using ice-cold water and ice-cold alcohol will increase your yield of DNA. The cold water protects the DNA by slowing down enzymes that can break it apart. The cold alcohol helps the DNA precipitate solidify and appear more quickly.
Make sure that you started with enough DNA. Many food sources of DNA, such as grapes, also contain a lot of water. If the blended cell soup is too watery, there won't be enough DNA to see. To fix this, go back to the first step and add less water. The cell soup should be opaque, meaning that you can't see through it. Cold water helps keep the DNA intact during the extraction process.
Cooling slows down enzymatic reactions. This protects DNA from enzymes that can destroy it. Why would a cell contain enzymes that destroy DNA? These enzymes are present in the cell cytoplasm not the nucleus to destroy the DNA of viruses that may enter our cells and make us sick. A cell's DNA is usually protected from such enzymes called DNases by the nuclear membrane, but adding detergent destroys that membrane.
The two most common enzymes used in meat tenderizer are Bromelain and Papain. These two enzymes are extracted from pineapple and papaya, respectively. They are both proteases, meaning they break apart proteins.
Enzymatic cleaning solutions for contact lenses also contain proteases to remove protein build-up. These proteases include Subtilisin A extracted from a bacteria and Pancreatin extracted from the pancreas gland of a hog. How much pineapple juice or contact lens solution should I use to replace the meat tenderizer? You just need a drop or two, because a little bit of enzyme will go a long way. Enzymes are fast and powerful!
DNA precipitates when in the presence of alcohol, which means it doesn't dissolve in alcohol. This causes the DNA to clump together when there is a lot of it. And, usually, cells contain a lot of it! For example, each cell in the human body contains 46 chromosomes or 46 DNA molecules.
If the human body is made of about trillion cells, each of which contains six feet of DNA, our bodies contain more than a billion miles of DNA! There is a protocol that would allow you to stain nucleic acids, but the chemical used would need to be handled by a teacher or an adult. So, for now, you'll just have to trust that the molecules precipitating in the alcohol are nucleic acids. That's exactly right! The procedure for DNA extraction is really a procedure for nucleic acid extraction.
Your DNA may last for years if you store it in alcohol in a tightly-sealed container. If it disappears it's likely because enzymes are still present that are breaking apart the DNA in your sample. Using more sophisticated chemicals in a lab, it is possible to obtain a sample of DNA that is very pure. DNA purified in this way is actually quite stable and will remain intact for months or years. Cells with more chromosomes contain relatively more DNA, but the difference will not likely be noticeable to the eye.
For example, plant seeds yield a lot of DNA because they have very little water in the cell cytoplasm. That is, they have a small volume. So the DNA is relatively concentrated. You don't have to use very many seeds to get a lot of DNA!
Peas are a good source of DNA because they are a seed. DNA is not soluble in alcohol; therefore, it makes the DNA strands clump together and become visible to the naked eye. DNA extracting solution mix about 1 tablespoon of dish detergent and 1 teaspoon of salt into 1 cup of water. Denatured alcohol eg. Mash the strawberry through the bag in your hand. Do not hit against the table as this may damage the DNA. Place the piece of gauze or cheesecloth over the opening of the cup, securing it with a rubber band.
Carefully pour the strawberry mixture into the cup making sure to catch the solids with the gauze. Take a dropper or spoonful of the liquid out of the cup and place in the test tube or smaller cup.
Add a dropper or spoonful of the alcohol to the test tube. Take care not to tilt or tip the test tube; do not mix the two liquids. Observe the line between the strawberry mixture and the alcohol. You will notice a white thread-like cloud appearing at this line. These are generally either solution-based or column-based. The extraction of DNA has become much easier with the emergence of commercial kits and the automation of the process. Such changes have both sped up production and increased the yield of DNA.
The ability to extract DNA is of primary importance to studying the genetic causes of disease and for the development of diagnostics and drugs. It is also essential for carrying out forensic science, sequencing genomes, detecting bacteria and viruses in the environment and for determining paternity.
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