Screening Hemoglobin for Sickle Cell Lab Activity

Concept or conceptual understanding:  This activity helps students understand how the shape of molecules determines how the cells themselves function in the circulatory system.  Through a gel electrophoresis experiment, the students experience how molecules (in this case, proteins) can be separated out by charge.

Real world connections (Relevancy):  Since sickle cell anemia has a strong racial component based on a regionally beneficial mutation, students see specifically how genetics play a role in a predisposition to a disorder.  Using a gel electrophoresis setup allows the students to see how biotechnology can be used in a diagnosis as a practical application of this technique.

AZ standards: (Science Standard Articulated by Grade Level – High School)

S1C1PO 4.  Predict the outcome of an investigation based on prior evidence, probability, and/or modeling (not guessing or inferring).

S1C4PO 4.  Support conclusions with logical scientific arguments.

S3C3 PO 3.  Predict the effect of a change in a specific factor on a human population.

S4C4 PO 1.  Identify the following components of natural selection, which can lead to speciation

·         genetic variability and inheritance of offspring due to mutation and recombination of genes

·         selection by the environment of those offspring better able to survive and produce offspring

S4C2PO 3.  Explain how genotypic variation occurs and results in phenotypic diversity.

S4C5PO 2.   Describe the role of organic and inorganic chemicals (e.g., carbohydrates, proteins, lipids, nucleic acids, water, ATP) important to living things.

Incorporation of inquiry:

Through a simple hands-on activity, students will demonstrate that the shape of things (in this case, beads) determines how well they function in specific situations.  This will lead to a discussion of the shape of molecules and how structure and function are related at the molecular level.  This concept will be repeated at various levels throughout the study of science.  Students will also be asked to investigate the idea of beneficial mutations as they explore the real world connections above.

Behavior objectives:

Demonstrate separation of proteins by agarose gel electrophoresis.

Determine whether a patient has sickle cell disease or is a carrier of the sickle cell trait.

Analyze inheritance patterns for those with sickle cell.

Prior knowledge necessary:

The students are given a reading to complete with question the day before the activity as a homework assignment.  This gives them some background information so that they will be able to participate in the class discussion prior to the lab.  A multiple choice pretest using a Classroom Performance System (CPS) will allow the teacher to facilitate a discussion on the reading as well as bring out important concepts related to structure and function of molecules.  The PowerPoint on how the gel electrophoresis works in this particular situation will help students understand the basics of this procedure, as it is likely that this will be something new to them.

Identify possible student preconceptions:

Students have a hard time visualizing the size of molecules, much less that they have specific shapes.  The CPS questions will help to address these misconceptions.  Because of popular television shows like CSI (Crime Scene Investigations), they have probably seen gels, but potentially have no idea how they were generated or how to read them.  The PowerPoint on this technique will address some of these questions.

Materials:

This is a prepackaged kit with materials necessary included. (Ward’s Natural Science kit # 36W 5350).  In addition, you must have (for each lab group) a electrophoresis chamber, power supply and micropipets (10μl).  If you would like to do a visual lab instead, we found the following:

http://k12education.uams.edu/scvlab/biochem.htm

I tried it once, and it seemed to work well, except for the conclusion step.

Safety:

Students should wear goggles, aprons and gloves during the gel electrophoresis experiment.

Lesson Description:

Set: Each pair of students is given a short length of tubing and two different beads.  One bead is spherical and the other is irregular. Then there is a “race” to see who can push their bead through the tubing the fastest.  Students are asked to white board their current knowledge of the circulatory system in a diagram fashion before the prelab discussion begins.

Prelab discussions:

            A PowerPoint has been prepared to introduce the idea of the size of molecules and cells and to facilitate a discussion of the homework reading.  This homework reading has been compiled from the Ward’s Biology background section and is in Microsoft Publisher format.  A Word document has also been prepared which includes a set of questions about the reading. 

            To demonstrate the randomness of genetics, we made a “luck of the draw” card set.  Several students will be asked to pick cards and then determine both their genotype and how that would be expressed.  They will have had some practice with this having done the homework assignment.  (This is a good activity to do while the gels are running.)

            Another PowerPoint has been prepared to introduce how gel electrophoresis works.  The kit contains explicit directions about the actual lab protocol, including what the teacher needs to do in preparation for the activity (make the gels and dilute the buffer).

Assessment:

            Since we took a slightly different approach from the kit, we created our own post lab writeup/assessment.