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Lesson 3: How do genes influence smoking behavior?

Overview:

Students learn how nicotine affects the brain and consider how genes involved in the reward pathway might affect smoking behavior. The genes in the UW Smoking Behavior Research Study are introduced, and students discuss why they are included in the study.

Class Time: 50-60 minutes

Additional resource on the neuroscience of addiction (several graphics may be helpful in the classroom): http://www.brainfacts.org/diseases-disorders/addiction/

Learning Objectives Evidence
Understand that certain genes might contribute to variability in smoking behavior and how this process might occur Students are able to draw and explain how a genetic change might change neurons in the brain and therefore affect a person’s physiology.
Understand that there are genetic and environmental components inherent in smoking behavior. In research teams, students explain possible genetic components that may affect their research topics in RPP-4.

 

Instruction:

Section A: Neurotransmission and the Effects of Nicotine

Part A1: Tracing Nicotine’s Path through the Body

1. Have students get into their research project groups. Hand out Blank_Student Sheet 3.1, Ask  them to draw where nicotine goes in the body after a person takes a puff on a cigarette.

2. As you discuss the pathway with the class, draw it on the diagram:

    • From the mouth, down the trachea to the lungs
    • From the lungs into the bloodstream to the heart
    • From the heart to all parts of the body, including the brain
    • From the blood to the liver, where it is broken down and excreted from the body through the kidneys

Make sure that students recognize that nicotine goes to the brain

Part A2: The Giant Neuron and Overview of Neurons and Neurotransmission

1. Show Diagram 3.1 to discuss the parts of the neuron (cell body, dendrites, axon, axon terminals, vesicles of neurotransmitter, and receptors) and the process of neurotransmission. Be sure to discuss how information is transmitted during neurotransmission— via an electric impulse within a neuron and via neurotransmitters between neurons.

2. Hand out Blank_Student Sheet 3.2 to be completed along with the Giant Neuron Model demonstration.

Giant Model Neuron Demonstration instructions: Review Making a Model of a Neuron and Background Reading on Neurotransmission

  1. Assign people to have different roles. You may need to demonstrate neurotransmission more than once so everyone gets a turn.
  2. Use large post-its to label the different cell parts (dendrites, cell body, and axon) on the neuron model.
  3. After completing Part 1C:PowerPoint presentation, as a class, use the model neuron again, this time to model how nicotine interacts with neurons in the reward pathway.
  4. Ask students which ping pong balls represent the nicotine (the ones tossed to the students holding      the “dendrite” ropes) and which are the dopamine (the ones in the “axon terminal” bucket).
  5. As a class, discuss where dopamine receptors are found (on the hands of the students catching the balls at the axon end of the model, which represent the dendrites of the next neuron) and where dopa decarboxylase is found (in the bucket at the end of the rope, which represents the axon terminals where dopamine is released)

Video- Neuron model demonstration

 

Part A3: PowerPoint Presentation: How Nicotine Interacts with the Brain

1. Hand out slides to Lesson3 powerpoint if you decide to review the reward pathway. Instructions are given in the PowerPoint. The PowerPoint presentation introduces students to the concept that different parts of the brain have different functions. During the PowerPoint presentation focus on the main concept—that genetic variation in the human population results in slight differences in the ways our bodies interact with chemicals like nicotine and can lead to variation in smoking behavior.

Section B: Viewing Genetic Questions in the Database

(This section is designed to show the genes, and their purpose, available to study in the student’s research project)

1. Access the database from your class computer and project it for the class to see (http://gsoutreach.gs.washington.edu/vlewrapper/view.html)

2. Click on Step 1.3: Hypothesis Testing on the left-hand side. View Questions 103-105 to show the genetic questions in the database.

3. Hand out Blank_Student Sheet 3.3 and complete while looking at the genetic questions in the database, the last two slides of the PowerPoint presentation, and Table 3.1- Genes included in Study. The questions in Student Sheet 3.3 are intended to guide student understanding of how variation in the three gene regions in the study might affect smoking behavior. This concept can be difficult for students, so this activity is best done as a class with . The intention of Question 3 is to show that everyone has two copies of the DRD2 gene, one on each chromosome 11. The purpose of Question 4 is to help students understand that different genotypes might affect the amount of DRD2 receptor made. In Question 5, students are then asked to consider how making less DRD2 receptor might affect their smoking behavior.

Video- Neurology lecture and discussion of genes in database

 

Optional Section C: How do Scientists Choose which Genes to include in a study

1. Display Diagram 3.2- Candidate Genes in Smoking Behavior Study to discuss how a scientist might select good candidate genes for a tobacco addiction study.

2. Discussion Questions:

How do you think scientists choose genes to study?

Students should discuss:

– They choose genes that make sense biologically. In order to do this, they need to understand something about the process they are studying.

– Scientists often look at other research studies that have been done by themselves or others. This often means reviewing the published literature to find out what has been learned on the same or a related condition.

Based on what we’ve learned about nicotine and the brain, how might DRD2 and DDC affect smoking behavior?

Students should discuss that DRD2 and DDC are necessary in the reward pathway and variation in them may be associated with variation in the effect of nicotine on the brain.

Based on what you gathered from the smoker profiles do think smokers are likely to have different variations of these genes than non smokers?

Students should bring up the variation in smoking behavior in the profiles. For instance, some people were able to quit easily and some are unable to quit, or some people felt a buzz or felt relaxed while others did not report these feelings related with smoking.

Section D: Could your research topic/factor have a genetic component?

1. It is important for students to think how genetics may be related to their research project topic. Ask each group to complete Blank_Research Project Page Lesson 3. They should discuss their responses as a group while reviewing the smoking behavior questionnaire.

HOMEWORK (optional):  If it is appropriate for the level of your class, ask students to complete Blank_Student Sheet 3.4 for homework.

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