Introduction
a) Background- What is DNA? Deoxyribonucleic acid or DNA is a molecule found in almost all cell types and living things. Its purpose is to carry genetic information and is responsible for everything that makes an individual unique. It also has the information for cells to perform all of their functions necessary to survive. Each person has a person combination of DNA, half from your mother and half from your father. DNA at the molecular level is a molecule shaped like a double helix that spirals and has rungs like a ladder, called bases. The bases are adenine, guanine, thymine, and cytosine, and each base functions in a code. Each of the bases are also connected to a sugar and a phosphate, creating nucleotides. When bases are pairing, adenine and thymine always pair and guanine and cytosine also pair. The four bases of DNA make codes that are comprehended by cells called genes, which make proteins that are the basis for almost all the inner workings of the body. The human body has more than 40,000 genes the come together for form the genome. Not all the genes in a cell are used. In the body, all the cells contain the same chromosomes, where the DNA information is located, but different cells read different genes from the chromosomes. It is important to remember that among humans, we share 99.9% identical DNA sequences and it is less that 0.1% sequence variation that distinguishes us from those around us, making humans not so different from one another. DNA does not directly make proteins. The templates for protein synthesis are ribonucleic acid or RNA and messenger RNA or mRNA. It is the job of mRNA to carry the information from the DNA to the ribosomes in a cell the create the protein. The proteins made give cells their traits.
b) Purpose- The purpose of this lab is to extract our own DNA from cheek cells we collect. We extract DNA to get a better look at what DNA looks like and to make it easier to study. This practice can be applied in the real world by scientists who precipitate DNA to study it, map it, compare it, sequence it, clone it, and have other uses for it as well.
c) Process- In order to extract our own DNA, we must first loosen our cheek cells by gently chewing the inside of our cheeks for about 30 seconds. After loosening the cells, we we swished a saline solution (0.9% saltwater) and spit the saline solution containing the skin cells back into the cup which we then transfered into a labeled 15 ml test tube containing 3 ml of water. After we added we added 2 ml of lysis buffer to the tube which breaks open and dissolves the cell membrane which is made of fats and the buffer serves as a detergent to remove the cell membrane. Then we gently invented the tube five times. Next we added 100 ml of protease to the tube to break up protein as well as DNAse which is a protein that kills DNA. The protease contains a salt solution as well, and by adding Na+, we neutralize the DNA and make it both hydrophobic and non polar. After we invert the tube a few times more. Then we place the test tube in a warm water bath at about 50 degrees Celsius to speed up the reaction and break open the cell membrane. Finally we add 5 ml of cold ethanol at a 45 degree angle to ensure that the DNA will not dissolve again. After 5 minutes, we slowly invert the tube five more times to aggregate. Finally, after the DNA is visible, we extracted it and placed it in a necklace.
Discussion
Although this lab was very informative, we did not have to prove a hypothesis or prove a postulate. However, there were many possible sources of error in the lab. First, we could have not swished the saline solution vigorously enough, therefore not extracting enough cells. When shaking the tubes to aggregate the DNA, we could have inverted the tube too vigorously and could have damaged the DNA precipitation.
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