The concentration versus absorbance graph yielded a straight line with R2 = 0.995. The limitation of pipetting skill can be seen clearly in the absorbance value of 1:250 solution, which slightly goes off the trendline. A possible error was that the required amount of liquid was not fully released to the tube. However, based on the linearity of the graph, the pipetting and dilution skills were acceptable. The DH5α in LB plate resulted in no bacterial growth, which indicates that some sources of error happened during the streak. Since there was no ampicillin presented, the bacteria should completely grow on the plate. One reason of error is that the loop used to streak the plate was too hot, which potentially killed the bacteria. Another possible …show more content…
The opposite result was expected for DH5α in LB/amp plate. In the presence of pUC18, the DH5α pUC18 developed resistance on LB/Amp plate, resulted in green (blue) colonies. In the high salt environment GVM, A.fischeri was able to grow as white colonies which resulted in bioluminescene. The DH5 α in LB plate and DH5α pUC18 in LB/Amp plate resulted in cloudy solution indicating a sign of bacterial growth. A.fischeri in GVM was a clear solution, meaning that there was no colonial growth. A possible source of error was that the liquid culture might not be vortexed before use. In the bacterial enumeration, there was an error occurred in preparing the dilution. An extra dilution was made because the student did not read the procedure carefully. The third solution used was a 9.0 ml-blank with dilution of 10-8, which lowered the expected concentration of the plate by a factor of ten. Despite of this error, as expected, moving from the most concentrated to the least concentrated solution, the colonies decreased by a factor of ten and all evenly distributed on the …show more content…
The first step in this process is to lyse the cell gently .This goal can be achieved by using Nuclei lysis solution, which breaks open the cell to release DNA from the nucleus. In the next step, RNase solution is important to degrade RNA to smaller components. To precipitate protein out, leaving DNA in the solution, Protein Precipitation Solution was used. To recover DNA, the addition of isopropanol, following by centrifugation, is necessary since DNA is insoluble in alcohol. Alcohol prevents water molecule to interact with the phosphate backbone of DNA, thus allowing cations to form ionic bond with the backbone to precipitate DNA out of solution1. However, at the same time, isopropanol might also precipitate the salt, which would contaminate DNA. To solve this problem, ethanol will be added in the last step to extract DNA. In ethanol, DNA needs to have higher concentration to precipitate, thus higher yield is expected. Since ethanol is more volatile than isopropanol, its addition to replace isopropanol will make the pellet faster to dry2 .To overcome the electrostatic repulsion caused by precipitating DNA, the negative charge of DNA can be shielded using monovalent cations such as 0.3M sodium or 2.5 ammonium ions and then adding