Lab report critiques

hey can you guys please read over our lab report and give some pointers!

Johan Conradie, Joe Lockett, Jennifer Cardonick
An Art, Which Needs Mastering: DNA Fingerprinting

*I'm not sure if this title is fitting. DNA fingerprinting is a trusted method and it's used a lot.. I don't think you want to say that it's an art that needs mastered. Try to focus your title on what your lab report is actually about. Make it a very brief summary of the paper.

In 1990 Sir A.J. Jeffreys first used DNA fingerprinting as way of identifying individuals and made a mark on genetics forever. By using a combination of electric currents, electrophoresis gel, dye and restriction enzymes, forensic identification and paternity tests could be done. The techniques require a steady hand and some practice to be done correctly but the results can confirm the innocence of many.

*You may want to include a little more information about the results and discussion of the experiment. Try looking at abstracts from other research papers and model yours from that.
~The point of an abstract is not to give background to your background section. Yes, you need to cover some of the basics here, but the larger point of an abstract is that an abstract gives a potential reader something VERY basic to look at, see what you did, what your conclusions were and if that information is useful to them. For future abstracts, you should focus on what you did, how you did it and what happened in the end. If you can focus on that, you can elaborate the in-between stuffs and your abstract will not only make sense, but it will introduce your paper well.

“The combination of variability among individuals and stability within an individual suggests that the patterns of fragment sizes revealed by specific probes might serve as useful individual identifiers, or DNA fingerprints.”(Cohen, 1990). Simply put DNA fingerprinting can identify individuals by their unique DNA “fingerprint”. This allows law enforcement to place criminals at the scene of their crimes, and can be used in paternity tests. Sir A.J. Jeffery was the first to perform the technique, which he published in a 1985 Nature journal article (Jeffrey, 1985). Restriction enzymes are used to cut DNA samples at specifies sequences. More specifically EcoR1 and Pst1 are the most commonly used. EcoR1 recognizes and cleaves the sequence G/AATTC at the slash (MeSH, 2008). Pst1 has a similar function in cleaving DNA. In this lab DNA fingerprinting was used to answer a question based on a fictional scenario. DNA from a crime scene would be compared to five suspects. The hypothesis being tested is; does the DNA sample from the crime scene match any of the suspects DNA? No judgment can be made on the hypothesis as of yet due to procedure error. The nature of the error will be described in detail at a later point.

Try and have your hypothesis be more of a statement and not a question. In general, having questions as your hypothesis do not work well in lab reports.

Good information in the background…I would suggest not saying "cleaves the sequence GAATTC at the slash" maybe say cleaves between the G and A bases. I would also suggest not saying the hypothesis is…Just state the hypothesis as a statement and the reader should be able to identify it as the hypothesis. However the info is sufficient. Nice job


During the procedure, at a crucial step where the DNA samples, mixed with blue dye, are injected into the wells of the gel, a mistake was made. Through sloppy technique, the DNA samples became contaminated with each other. This was only realized after electrophoresis was completed, and the gel was stained. Considering this error, a proper conclusion could not be made, and the hypothesis “Did the DNA sample from the crime scene match any of the suspects DNA?” could not be answered. Looking to the future of this experiment, change will need to be made. Proper technique will need to be cemented down for this experiment to answer any question. Since the error was human and assuming no other errors were made, the experiment should simply be repeated. In this particular experiment plasmids where used instead of human DNA. Plasmids are better suited for the electrophoresis apparatus used in this experiment than human genomes were. Plasmids are DNA molecules, typically found in eukaryotes such as bacteria, capable of replicating independently from the chromosome for the purpose of transferring genetic information to other cells. Compared to human DNA, plasmids are relatively small in size. DNA molecules are commonly expressed in the units known as kilo bases or kb, representing 1000 base pairs. Plasmids can be anywhere from .5 to a few hundred kb. Human DNA, however, is made of several hundred kb and is too large for PCR. PCR is the step in electrophoresis which “unzips” the DNA that is soon to be cleaved by restriction enzymes that were added.

For the first two sentences i would fuse them and say something like…Through human error, the DNA samples were unintentionally mixed together when pipetting them into the gel. Also, bacteria are prokaryotes, and im not sure if we did PCR in this lab…if we did let me know…but PCR involves amplifying the DNA, so i would exclude this from your conclusion


COHEN, J. E. 1990. DNA fingerprinting for forensic identification: potential effects on data
interpretation of subpopulation heterogeneity and band number variability. Am. J. Hum.
Genet. 46:358-368.

Jeffreys, Alec J., Victoria Wilson, and Swee L. Thein. "Hypervarialble 'minisatellite' regions in Human DNA." Nature 314 (1985): 67-73.

Lynch, Michael. "The Similarity Index and DNA Fingerprinting." Oxford Journal 7 (1990): 478-84.

"MeSH Descriptor Data." Medical Subject Headings. National Libary of Medicine. 19 Jan. 2009 <>.

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-ShareAlike 3.0 License