DNA Precipitation Lab Discussion

A) Discussion:
The resluts of the DNA precipitation lab were approximately what I had predicted. My earlier predictions included that I would receive a transparent little knot of precipitated DNA, and that part was true. My group and I performed every part of the procedure correctly, and precisely, which allowed each of us to obtain favorable results.

B) Possible Sources of Error:
-Ate a chicken sandwhich during brunch, and precipitated the DNA of a chicken.
-No cheek cells were extracted from mouth, so there was no DNA to precipitate.
-Lab table member accidently contaminated the lysis buffer pipette with his or her DNA by dipping pipette into their test tube.
-The inverting of the tube was not intense enough, and the lysis buffer was not thoroughly mixed in. Thus the cell membranes were not dissolved and the DNA never left the cell.
-We did not add enough Protease, and the DNASE survived to kill all of my DNA.
-The inverting of the tube with the protease was too intense, and all of he DNA stuck to the sides of the tube.
-I accidentally removed the tube from the hot water bath too soon, so the necessary chemical reactions did not occur.
-Read the directions incorrectly, and added 10 microliters instead of 10 milliliters.
-When placing the precipiataed DNA in the supercool class necklace, applied too much pressure to the glass case itself and the glass broke in my hand.

Our Own Slice Of Immortality; The Extraction and Precipitation Of Our DNA

A) For all living  organisms DNA is present, and for some, DNA is the code for life. However, not until fairly recently have scientists known DNA's genetic importance. In human beings DNA codes for such traits as hair color, eye color, height, facial features and blood type. In 1953, James Watson, Francis Crick and discovered the structure of DNA with the help of Rosalind Franklin. The scientists built a model of DNA, which was the first accurate model of its time. Their model described that DNA a double helix, connected by four nitrogenous base pairs, adenine, thymine, guanine, and cytosine. Each base is connected to a sugar and a phosphate group, which act as the backbones of the structure. The entire unit is called a nucleotide. The DNA of the cell is found in the nucleus of almost every cell of the human body (because an enzyme called DNASE evolved to kill all DNA outside of the nucleus in case the DNA was viral). The DNA is coiled up around histones (proteins) and organized into structures called chromosomes. There are 46 chromosomes in human cells, and all of the genetic information contained in the 46 chromosomes represents the genome. A gene is a section of DNA which codes for a certain trait. Humans receive their DNA from their parents, half from the father, and half from the mother.

B) The purpose of this experiment is to precipitate our own DNA. Precipitating our DNA will make it visual, and we will have the chance to view our very own DNA. This allows us to compare it, and would allow us to test it, clone it or sequence it.

C) To precipitate our DNA, the first objective we must complete is to extract our cheek cells by rinsing our mouths vigorously with a 0.9% saline (isotonic) solution. The solution will allow for quick extraction, and the cells will not burst in an isotonic solution. We will then add the lysis buffer (soap), and invert the tube several times to mix in the buffer completely. The lysis buffer will break open the cell membrane by dissolving the phospholipids in the plasma membrane. After the addition of the buffer, protease will be added and the tube inverted to spread the Protease throughout the test tube. Protease had the purpose of destroying DNASE before DNASE can kill our DNA. DNA has a negative charge, and water has a positive charge. Because of this, DNa is hydrophilic (attracted to water) and will dissolve in water. To counter this, we will add salt which will neutralize DNA's charge. Without a negative charge, DNA will become hydrophobic and non-polar. Our DNA will then be placed in a hot water bath to speed up the reaction time and break open the cell membrane. To finish this process we will add cold ethanol to precipitate the DNA. Ethanol is the preferred substance because of it's lower freezing point. It will become colder while staying a liquid.

Yogurt Lab Discussion

A) The predictions that my lab table gave were approximately what we received as results. In tube 1 (the milk), the milk never transformed into yogurt, because there was no addition of a probiotic. Tube 1 was acting as a control, a basis for what the milk was to look and smell like, and also to give the lab researcher an idea of the texture. Some of the physical properties of tube 1 include: a semi-liquid texture, a smell of slightly sour milk, a white color, and a pH of 7. In tube 2, the milk and the addition of the yogurt (the probiotic), transformed the milk and yogurt into yogurt. Tube 2 was a variable, because the results of the milk added to the yogurt could have either changed or remained the same. The purpose of a variable is to measure the transformation and possible change that a certain experiment could cause. The properties of tube 2 include: a semi-solid texture, a smell of yogurt, a white color with a transparent film at the top, and a pH of 4. Tube 3 was composed of milk, yogurt, and ampicillin. This tube was also a variable in this experiment, as we were trying to figure out if yogurt could be produced with the addition of an antibiotic. The end result was no, because the ampicillin killed the bacteria in yogurt which did not allow the transformation from milk to yogurt to occur. The physical properties of tube 3 include: a semi-liquid texture, a smell of sour milk, a white color and a pH of 7. In our final test tube, tube 4, we tried using a different type of bacteria to make yogurt. This was also a variable, because E.Coli is another type of bacteria, and our lab group was attempting to find if any type of bacteria could create yogurt. E.Coli did not produce yogurt, some of the physical properties of tube 4 are: a semi-liquid texture, an unattractive smell (bad smell), a white color and a pH of 7. The yogurt up in the front of the classroom is worthy of mentioning, as it acted a control for tube 2. The yogurt had a pH of 4, and a yogurt smell, a white color, and a semi-solid texture. Our table succeeded in creating yogurt.

B) Possible Sources of error include:
- Accidentally adding ampicillin to tube 2, which causes all the bacteria to die. Which means no yogurt is produced.
- We used the same yellow rod to add yogurt to all 4 of our tubes, and we add ampicillin to tube(s) 1, 2, or 4 on accident.
-The vortex could have shaken the tubes so violently that the ampicillin stuck to the roof of the tube and we created yogurt in tube 3.
-The hot water bath was so hot that the DNA strands in the bacteria's nucleoids denatured, thus making the process of yogurt making impossible.
- The hot water bath was not hot enough to pasteurize the yogurt, so bad bacteria survived and spoiled the milk or yogurt
- The vortex did not move enough to thoroughly mix in the contents of tube 2, tube 3, or tube 4 so either yogurt was not produced, ampicillin did not come into contact with the yogurt and yogurt was produced, or the E.Coli was just pooled at the bottom
- We dropped all of our tubes on the ground and bad bacteria entered all of the tubes and spoiled the various results