Human Biology -Feedback Loops and Clockwork Genes

M5 Laboratory Report Form

This lab exercise walks you through several animations and a virtual lab and gives you questions to answer about each exercise. You should read over the questions about each animation or lab before you watch it or perform it, so you will know what to watch for.

• The first animation is an introduction to positive and negative feedback.
• The second video contains several examples of feedback mechanisms.
• The third animation is about the leptin feedback system.
• The fourth part of this lab is a virtual lab, involving clockwork genes in transgenic flies.

Complete this Laboratory Report Form, save it to your hard drive, and submit it in the Module 5 Lab area.

1. Positive and Negative Feedback:

Click on the following link, watch the animation, and answer the following questions:

http://highered.mheducation.com/sites/0035456775/student_view0/chapter40/positive_and_negative_feedback.html

1. Explain how a negative feedback loop works.

2. Explain how a positive feedback loop works.

3. Which type of feedback loop is more common in the body? (Hint: think about the goal of homeostasis)

4. Describe, in detail, the positive feedback loop illustrated in the animation.

5. Describe, in detail, the negative feedback loop illustrated in the animation.

1. Feedback Loops:

Click on the following link, watch the video, and answer the following questions:

http://tll.mit.edu/help/feedback-loops

1. Describe the thermoregulation feedback loops illustrated in the video.

2. Describe the positive feedback loop illustrated in the video.

3. Identify the receptor, control center, and effectors in blood glucose regulation.

4. Identify the parts of the feedback loop that break down in Type I diabetes.

5. Identify the parts of the feedback loop that break down in Type II diabetes.

1. Leptin Feedback Control System:

Click on the following link, watch the animation, and answer the following questions:

http://www.hhmi.org/biointeractive/leptin-feedback-control-system

1. Describe the appearance of leptin production during normal eating in the animation.

2. What happens to your leptin production during dieting? Why?

3. What is the body’s response to low leptin levels?

4. Describe the appearance of leptin production during over-eating in the animation.

5. What is the body’s response to high leptin levels?

1. Transgenic Fly Virtual Lab – Clockwork Genes:

Click on the following link, perform the virtual lab, and answer the following questions:

http://www.hhmi.org/biointeractive/transgenic-fly-virtual-lab

1. What is the purpose of this lab? Why do you use transgenic flies?

2. Explain the procedure you used for making transgenic flies.

3. What does the period gene normally control for the fly? Why is it useful for this lab that the period gene is linked to the luciferase gene?

4. What is the purpose of incorporating the red eye allele into the construct DNA?

5. Describe your results from the mating of injected white-eyed flies with non-injected white-eyed flies and explain the significance of these results.

6. What does the carbon dioxide do to the flies?

7. During what time of day did peak light emissions peak and trough?

8. Describe what happened when you measured per-Luc gene expression while keeping the lights off, and explain its significance.

9. Describe what happened when you measured per-Luc gene expression while turning lights on and off, and explain its significance.

10. Explain what you found when you examined different fly body parts for per-Luc gene expression, and explain its significance.