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