Writing a lab report

Writing a Lab Report

You will write two lab reports on the lab project during the semester.  The first lab report will cover the procedures conducted in Weeks 3-7 (Transformation through Agarose gel electrophoresis).  The second lab report will incorporate edits suggested by instructors, all procedures covered in the first report and include the additional material from weeks 8- 12 (Transfections through western blots). In other words, you are adding to your first report and updating all sections to include the new information.  The first report should not be viewed as a draft, it is a final version of a first report.

Reports are to be written by lab teams. All team members should contribute equally. Lab reports are to be submitted electronically by email, to both SAC and JCP: for the mid-term report, please submit your document in Word, as that makes it easier for the instructor to make comments and corrections on the document in “Track Changes” mode. (However, please do have a PDF version available on request, in case there are formatting issues with the figures.) For the final lab report, in which commentary is expected to be less extensive, either Word or a PDF is acceptable. Please include your team name in the electronic file name; although I can certainly write it in after the fact, it’s much easier and less time-consuming if it’s there from the very beginning. Hard copies are typically not expected.

Organization

Lab reports are to be written in the form of a scientific research article. A well written lab report accomplishes several things; for example, students learn how to write professional- sounding reports that communicate their scientific findings clearly. Also, the process of preparing for and writing the lab reports helps to solidify students’ understanding of the work they did.

The following sections (with the exception of Title Page) should be identified by a heading:

Title page: Whether a separate first page, or incorporated into the first page, the “Title” section should contain the following: The title for your report; the names of each student author and the team name; the date, course name and other relevant information (for ex., “Mid-term” or “Final” lab report).

Abstract: This is a concise (one paragraph) summary of the rationale, methods and findings of a project. To get a perspective on the importance of the Abstract, know that in scientific journals this is often the only part of a scientific paper that will be read by many people. Therefore it is important that all main points are expressed in this section; think of it as an actua ‘mini-report’, encompassing the lab report in a single paragraph. It is advisable to write this section last, after you have written the body of the report.

Required elements for Abstract (in condensed writing style):

  1. Background statement or 2 on the topic in general, including any unanswered questions that you are about to address in the report.
  2. Description of what you actually did: write out the names of the various techniques (eg, PCR to amplify the gene/region of interest, DNA isolation from cells by silica gel chromatography, agarose gel electrophoresis of PCR products to separate by size, etc.).
  1. Actual RESULTS!! eg, Sizes of bands in base pairs or kilodaltons, appearance of plates (i.e., number of colonies), DNA concentration, etc.
  2. Concluding statement(s) indicating some level of interpretation of your results: eg, “the sizes of our PCR products indicate that we have cloned the correct gene, as confirmed by the digest results”…or, “contrary to expectations, I am null for the phenotype in question”-whatever is appropriate for the particular study. But do be concise here!

 

Introduction: In this section you should describe the background to the project, essentially by expanding upon the opening statements of the Abstract. i.e., What is the project about, why did you conduct these studies, what questions did you hope to answer or what hypotheses did you test, and how does the study relate to progress in this field? (This does not need to be a comprehensive, excessively lengthy review, however.) In this section, you prepare the reader for the remainder of the document, but you need not (and should not) summarize the results or give away the findings. This section should not be a repeat of the Abstract. A well written ending to the Introduction will “lead in” to what you are going to present in the remainder of the report.

Materials and Methods: This is the section where you describe, in a relatively concise manner, the reagents, equipment and methods that were used so that another researcher could complete the study. Assume that you are writing this for peers who are somewhat familiar with the techniques, but who do not necessarily know much about your project or area. Using complete sentences as opposed to bulleted lists, write “abbreviated” protocols that make the methods clear, but NOT the step-by-step protocols that are better suited for the lab notebook. Include the most important components of the experiment, along with a brief explanation of why you are doing it.

Preferably, each technique/procedure should be described under its own sub-heading (i.e., “Agarose gel electrophoresis”, “PCR of the Luciferase insert”, Bacterial Transformation”, “DNA purification”, etc.). In general, we look for reaction times and temperatures to be presented (“37 deg for 1 hour; room temp for 30 min”), the quantity of the most important reagents in a reaction tube (ie, µg of DNA where applicable, concentration in molarity of PCR primers, concentration in units of enzyme) and the total volumes of a reaction (“..in a total reaction volume of 50 ul”). Be definitive about what you are trying to communicate, and use transitional sentences (at end of one section or beginning of another) to make it clear why you are carrying out a particular sequence of procedures.

 

Results: In this section you should describe the results that you observed, including your own interpretation of the results; for example, rather than just writing “..bands of 650 bp were observed”.., go a step further and say, “…bands of 650 bp were observed, making it clear that the correct PCR product was amplified”.

Along with the written description of results, numerical data is best presented in tables and/or graphs/charts, whereas images of gels, western blots, plates of bacteria or cultured cells, etc. should be presented as clearly labeled figures. Tables and figures of all types should have descriptive “legends” written beneath them, called “table legends” or “figure legends”, respectively, which are usually in smaller print to save space and to set them apart from the body of the text. Table and figure legends clarify/summarize the content being presented (see below for more detail).

A figure or table legend typically begins with a title for the figure/table, such as “Agarose gel electrophoresis of PCR products”, “Quantitation of luciferase activity in transfected cells”, “Changes in A280 with increasing protein concentrations”, “Dose-Response curve of proliferation with EGF stimulation”, “The effect of buffer on pH”, etc. The information presented in these tables and figures must STILL be cited in the text of this section. Tables and graphs by themselves are not sufficient for a Results section.

Tables and Figures are to be numbered sequentially: “Table 1, Table 2, Figure 1, Figure 2”, etc. Even if you have only one figure or one table, it is still “Figure 1” or “Table 1”. , etc.

  1. Tables. Data that are difficult to visualize through text descriptions alone are usually best represented in a table. Tables should have a legend beneath them that summarizes the content clearly to the reader, unless the meaning is completely obvious in a given situation. The reader should not have to figure out what the columns or rows indicate.
  2. Figures and Graphs. All figures, no matter what type, must be appropriately labeled to provide clarity for the reader in terms of the most important data; for ex., in figures of gel images, lanes should be either numbered or (if the author prefers) identified with text; indicate positions (in bp) of at least some molecular weight markers; if there is a band on a gel to be singled out from other bands, it is sometimes helpful to include an arrow pointing to the band of interest. Avoid putting these labels ON the image itself; instead, label the immediately surrounding areas. Axes of graphs should be clearly labeled and the units of measurement shown; a key should indicate the meaning of different types of labeling; for ex., “solid color = treated; open bars = untreated”, or “solid line is data with growth factor, dotted line is data with placebo”. (That kind of information can either be adjacent to the figure itself, or incorporated into the written figure legend, see below.)

 

Figure and table legends.

Each figure should have a descriptive (but concise) figure legend that clearly states what information the graph or image conveys. For a gel figure legend, you would probably include, for ex., “Lane 1, DNA marker; Lane 2, Student DNA; Lane 3, Positive control”, and anything else that helps the reader to skim the figure and get the main points. If figure legends are written properly, the figure could almost “stand alone” without the text (although you would still need to describe the contents of the figure in the text).

The content of a table legend, beyond the title, will depend more on the specific content of the table and the degree to which additional clarity is needed; to this end, additional information in the legend is left to the discretion of the authors. Perhaps a summary of the main points of the table is all that is needed, in certain situations. The goal is for each figure and table (plus its legend) to be a ‘stand- alone’ presentation of a set of data points, so the legend should complete the presentation.

 

Discussion: This section is where you will elaborate on your interpretations of the results that you obtained, and explain how this is consistent or not with what was expected, based on previous work by others (if applicable). Possible sources of error should be discussed here, along with anything that was learned in the process. This is where you pull the whole story together for the reader and bring your results to some logical conclusions and thoughts for future directions. You may indicate, for example, that your results are consistent with, or are not consistent with, a prevailing hypothesis in the field. What would be the next steps in this project for you or another scientist?

Some authors prefer to combine the Results and Discussion sections into one, and for most student lab reports, we believe it is the easier way to proceed:

Results and Discussion: There are no strict rules on organization of a combined Results/Discussion section, but often this consists of a section-by- section description and interpretation of results, placing them in the context of the project as a whole (and the topic in general). Depending on your writing style, you may wish to follow up with a ‘re-cap’ paragraph at the very end that pulls it all together. (“So in conclusion, we observed …”)

 

References (or Bibliography): In this section you should list any literature sources (including the lab manual) that have been cited in the body of the report. Please use a professional format such as: Last name of author (in order as listed in the paper), first name or initial, comma, subsequent authors (in the same manner), year of publication in parentheses, Title of paper, journal or book, volume and page numbers (or for books, publisher).

  • Insert citations within the body of the paper at the appropriate places (when referring to the study). Typically, when citing a specific manuscript that is listed in your bibliography, you will insert the author(s)’ names and the date of publication at the end of the relevant sentence (Jones, D. et al1, 2005). Alternately, if your list of citations is numbered, you will insert the appropriate number in parentheses. Any fact that you are including that is not widely accepted must be backed up with a citation to the literature. You do NOT need to cite the lab manual continuously in the body of the paper, although it should certainly be listed in your bibliography.

 

Passive or Active Tense: Use of the passive tense is preferable for certain sections of the lab reports, and more in keeping with the prevailing writing style for scientific research papers. In particular, you will most likely use passive tense in the Materials/Methods and Results sections, where you are describing the science (and where identity of the persons performing the experiments is understood to be you). For example, “DNA was found to be heterogeneous at the relevant locus”, is preferable to “We found the DNA to be heterogeneous at the relevant locus.”) HOWEVER: it is OK to occasionally use “we” in these sections, when it is necessary for clarity or just to introduce variety in your sentence structure. “The author” is a good substitute for “I”.

1 For citations by name within the body of the paper, “et al” is typically used as an abbreviation for “and others” when there are more than two authors. Naturally, if “Jones, D.” is the sole author, you will omit the “et al”. If there are exactly two authors, it is fine to write “Jones, D. and Smith, P., 2005”). Be consistent in all your citations. In the list at the end, however, please do write out all the names as opposed to “et al”.

Use of the active tense (“we”) is expected in the Introduction and Discussion sections, when you are informing the reader of what YOU have done (or

what YOUR interpretations are), as distinct from the other studies you have cited for background and context. For ex., a typical introduction may end with “Our approach in the current study was to extend the findings of the Smith et al group, and search for inhibitors….” ; “We have carried out experiments on a 3-dimensional model of skin in order to more accurately evaluate the efficacy of drug A….” etc. In these sentences, as part of the Intro and/or Discussion, it is important to distinguish your work from the work of others, requiring “active tense” for clarity.

Miscellaneous Lab Report Tips:

Abbreviations. If a standard abbreviation for a lengthy word(s) is desirable, proceed as follows: The first time that the word appears in the report, it should be spelled out with the abbreviation in parentheses just after it. After the first appearance, you may use only the abbreviation. An exception: if you do this in the Abstract; you may use the abbreviation for the remainder of the Abstract itself, but please spell out the word one more time in the body of the report followed by its abbreviation. From then on, you may use only the abbreviation. (i.e., Treat the Abstract as if it were a separate document.) A list of abbreviations on a separate page (or in a footnote) may be helpful.

An example: “One study has shown that monoclonal antibodies (mAbs) may be therapeutic….”

For the remainder of the paper, “mAbs” may be used instead of “monoclonal antibodies”.

(One exception to this rule includes the widely accepted abbreviation, “dNTP”; you need not write out “deoxynucleotide triphosphate”. If you are in doubt in a particular situation, just ask one of us or be conservative and spell it out initially.

Clarity. It is critical that the report is written in a comprehensible and concise way. The reader shouldn’t have to spend time trying to figure out what you mean- it should be clearly stated.

Content. Both the mid-term and final lab reports are based on the long- term lab project that begins after the 2nd (or 3rd) week of Intro lab practices. As you write the mid-term report, include the experiments and findings up to and including the last section indicated by us (typically after agarose gel electrophoresis); even if we have gone “ahead” some with the project at the time of writing, you have to write as though we haven’t. The final lab report is comprehensive, in which you will not only modify the first draft as indicated/suggested, but also complete it by including the final series of experiments. (i.e., The final lab report covers the entire project.)

Length. There is no set length for the report. The abstract is typically one paragraph, and Intro is typically 3-4 paragraphs; however, the length will vary between groups.

“Do’s” and “Don’ts” for writing lab reports

  • DON’T write a chronological narrative; ex. don’t present your work as a weekly journal of lab activities (Wrong: “First we transformed the DNA, then the next week we purified plasmid DNA… then the third week, we digested the DNA with restriction enzymes”… NOT!)
  • DON’T present “results” for each and every experimental procedure, when there are no concrete ‘true’ results to present!
  • DON’T obscure gel images with (for ex.) annotation software that places horizontal lines throughout or circles around bands of interest; keep arrows, asterisks, etc. adjacent to image.
  • DON’T copy/paste tables and charts from the lab manual that indicate reaction components or tube contents (ex., for the restriction digests, PCR reactions, transfection experiments). Write it out in your own words, concisely, using whole sentences.
  • DON’T put extensive experimental detail in the Introduction when describing your project. Save that for the later sections of the report.
  • DO write in a clear, engaging manner. Make us “want” to read your paper!
  • DO stay in the past tense in Materials and Methods, when describing what you actually did.
  • DO present your findings in an overall positive tone, even if your data are not “perfect”; emphasize the learning experience and/or what could be discerned from your work. Leave the reader with a good impression of you and your work.

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