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The Method of Science in General Biology Laboratory - Case Study | HBIO 112, Lab Reports of Biology

Material Type: Lab; Class: General Biology; Subject: Biology; University: Morehouse College; Term: Unknown 2004;

Typology: Lab Reports

Pre 2010

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General Biology Laboratory BIO 112 Morehouse College
1
Laboratory Orientation Case Study
There are two parts to this case study. Your typewritten responses to both parts are
due in laboratory next week.
Case Study Part 1: The Method of Science
In Class: Work in groups of four students and address the Scientific Methods issues and
the Academic Honesty issues. There will be an open discussion of these issues after the
groups.
Homework: Write responses to the Scientific Methods questions and write an original
summary of the research article. Your typewritten responses must be in your own words.
The following is the complete abstract from “Role of actin filaments in the axonal
transport of microtubules” (Hasaka, Myers and Baas, 2004):
“Microtubules originate at the centrosome of the neuron and are then released for
transport down the axon, in which they can move both anterogradely and
retrogradely during axonal growth. It has been hypothesized that these movements
occur by force generation against the actin cytoskeleton. To test this, we analyzed
the movement, distribution, and orientation of microtubules in neurons
pharmacologically depleted of actin filaments. Actin depletion reduced but did not
eliminate the anterograde movements and had no effect on the frequency of
retrograde movements. Consistent with the idea that microtubules might also
move against neighboring microtubules, actin depletion completely inhibited the
outward transport of microtubules under experimental conditions of low
microtubule density. Interestingly, visualization of microtubule assembly shows
that actin depletion actually enhances the tendency of microtubules to align with
one another. Such microtubule-microtubule interactions are sufficient to orient
microtubules in their characteristic polarity pattern in axons grown overnight in
the absence of actin filaments. In fact, microtubule behaviors were only chaotic
after actin depletion in peripheral regions of the neuron in which microtubules are
normally sparse and hence lack neighboring microtubules with which they could
interact. On the basis of these results, we conclude that microtubules are
transported against either actin filaments or neighboring microtubules in the
anterograde direction but only against other microtubules in the retrograde
direction. Moreover, the transport of microtubules against one another provides a
surprisingly effective option for the deployment and orientation of microtubules in
the absence of actin filaments.”
Scientific Methods
1. What are the questions and problems being addressed by the research described in
this article? Identify both the narrow and the broader issues addressed by this
research.
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Laboratory Orientation Case Study There are two parts to this case study. Your typewritten responses to both parts are due in laboratory next week. Case Study Part 1: The Method of Science In Class: Work in groups of four students and address the Scientific Methods issues and the Academic Honesty issues. There will be an open discussion of these issues after the groups. Homework: Write responses to the Scientific Methods questions and write an original summary of the research article. Your typewritten responses must be in your own words. The following is the complete abstract from “Role of actin filaments in the axonal transport of microtubules” (Hasaka, Myers and Baas, 2004): “Microtubules originate at the centrosome of the neuron and are then released for transport down the axon, in which they can move both anterogradely and retrogradely during axonal growth. It has been hypothesized that these movements occur by force generation against the actin cytoskeleton. To test this, we analyzed the movement, distribution, and orientation of microtubules in neurons pharmacologically depleted of actin filaments. Actin depletion reduced but did not eliminate the anterograde movements and had no effect on the frequency of retrograde movements. Consistent with the idea that microtubules might also move against neighboring microtubules, actin depletion completely inhibited the outward transport of microtubules under experimental conditions of low microtubule density. Interestingly, visualization of microtubule assembly shows that actin depletion actually enhances the tendency of microtubules to align with one another. Such microtubule-microtubule interactions are sufficient to orient microtubules in their characteristic polarity pattern in axons grown overnight in the absence of actin filaments. In fact, microtubule behaviors were only chaotic after actin depletion in peripheral regions of the neuron in which microtubules are normally sparse and hence lack neighboring microtubules with which they could interact. On the basis of these results, we conclude that microtubules are transported against either actin filaments or neighboring microtubules in the anterograde direction but only against other microtubules in the retrograde direction. Moreover, the transport of microtubules against one another provides a surprisingly effective option for the deployment and orientation of microtubules in the absence of actin filaments.” Scientific Methods

  1. What are the questions and problems being addressed by the research described in this article? Identify both the narrow and the broader issues addressed by this research.
  1. What is the hypothesis that was tested in this study and what outcome can we predict based on this hypothesis? Describe an appropriate Null Hypothesis and prediction for this study.
  2. Describe the experimental procedure used by the researchers and describe an appropriate control treatment. What is the purpose of a control treatment?
  3. What were the specific results of this study and what do those results lead us to conclude? Academic Honesty The following is a summary of the above research article written by a freelance writer who plans to submit it to the science editor of a newspaper: Hasaka, Myers and Baas (2004) in a study titled “Role of actin filaments in the axonal transport of microtubules” published in The Journal of Neuroscience analyzed the movement, distribution, and orientation of microtubules in neurons pharmacologically depleted of actin filaments. The depletion of actin reduced but did not completely eliminate the anterograde movements of microtubules and had no effect on the frequency of retrograde movements. However, actin depletion completely prevented the outward transport of microtubules under experimental conditions of low microtubule density. Interestingly, photographs of microtubule assembly shows that actin depletion increases the tendency of microtubules to align with one another. Such microtubule-microtubule interactions are sufficient to orient microtubules in their characteristic polarity pattern in axons grown overnight in the absence of actin filaments. The researchers concluded that microtubules are transported against either actin filaments or neighboring microtubules in the anterograde direction but only against other microtubules in the retrograde direction. Furthermore, the transport of microtubules against one another provides a very effective means for the deployment and orientation of microtubules in the absence of actin filaments.
  4. Would it be dishonest for the freelance writer to submit the paragraph above as his own work (compare this paragraph to the Abstract above and explain why you do or do not think this paragraph is dishonest)?
  5. What must a writer do to ensure that their writing is original while giving appropriate credit to the authors of new information or ideas?
  6. Why is academic honesty important? What do you expect of your professors?
  7. What are the consequences of academic dishonesty at Morehouse College? Literature Cited Hasaka, T.P., K.A. Myers, and P.W. Baas 2004. Role of Actin Filaments in the Axonal Transport of Microtubules. The Journal of Neuroscience. 24(50):11291-11301.

In Class: Each of you will (individually) use Excel to prepare a graph of these data (Figure 1) with fully labeled axes, a descriptive title (Figure 1 is not the title), and a prose legend (complete sentences). Before you prepare your graph, discuss which is the dependent variable and which is the independent variable? Which variable type should be plotted on the y-axis? What do these data suggest about the relationship between weight and heart rate in humans? Homework : Use library resources to write an Introduction about the physiological relationship between weight and heart rate, cite your references in the text of your writing (author, year), and prepare a Literature Cited following the guidelines given in the laboratory syllabus. Typewritten responses due in laboratory next week. This case study was prepared by L. Blumer with assistance from V. Haftel, 1/2005.