3.C Approach: For selection of the topics for the laboratories, grade-specific standards that were created by the American Association for the Advancement of Science (AAAS) were used. Based on their Project 2061 database, focus was put on the topics with prevalent misconceptions (http://assessment.aaas.org/). According to this database the following questions showed prevalent wrong answers and misconceptions in grades 6-8 (Table 1).
Table 1: Common student misconceptions regarding genetics and DNA
1.) The genetic code is a sequence of subunits in a DNA molecule.
2.) Four different types of nucleotides are used to make up a DNA molecule, not ten, or twenty.
3.) Nucleotides (not amino acids, proteins, or fatty acids) are the subunits that make up DNA molecules.
4.) Both an organism’s physical characteristics and its behaviors could be affected by the information in the DNA molecules.
The main learning points (targeting the above misconceptions) are presented to students at the beginning of the session. Specifically these learning goals are 1.) To identify what DNA is and what it is made of (targeting questions 1-3) and 2.) Why and how we can study DNA in the laboratory (targeting question 4).
In order to approach these topics two main activities were developed. The first involved a hands-on activity with magnetic DNA molecules to discover what DNA is made of. Each student is given a single magnetic nucleotide molecule. During the laboratory period they are asked to turn to a neighbor and attempt to match the molecules they are given. A few minutes is provided so that students can discuss what is going on with the molecules and then the class is brought back together to gain conclusions. As the instructor I ask the class what their findings are. Specifically: What molecules paired together perfectly? (Students then raise hands to identify the matches of A-T and G-C). Did anyone create matches other than A-T and G-C? (The magnets will still bind incorrectly, however there will be exposed magnets showing an incorrect pairing). How do those matches compare to the A-T and G-C pairs? (Students then discuss and identify the exposed magnets or bonds between the mismatch pairs). This then transitions to a discussion of why the nucleotide order is important.
The second activity consists of a simulation of gel electrophoresis, a common technique used by researchers to study DNA. Prior to the activity students are presented with facts about DNA sequence (i.e.- The DNA sequence of two different individuals is 99% similar). Thus fostering the ideas that small differences in the DNA sequence can affect characteristics ranging from appearance to health issues. Based on this, there is a growing importance to study these small differences.
The basic mechanisms of gel electrophoresis are presented including a diagram to explain how it works (Figure 1).
Figure 1: Mechanism of gel electrophoresis
From this explanation students are able to gain that the negatively charged DNA migrates towards the opposite positive charge. Samples that have smaller DNA fragments (fewer nucleotides) will migrate farther through the gel before getting stopped. Students are then broken into small groups to load sample “DNA” into a gel. Food coloring is used to simulate a sample and students are told that each color of DNA is a different size. Prior to loading the gel they are asked to use the scientific method to hypothesize which sample will move farther through the gel. Then, they are able to work in groups to load the samples. Once loaded, the students return to their seats and the electricity is allowed to flow through the gels to allow sample migration.
Final discussion is then encouraged with a review of the main learning points from the activity.
Since the students will have diverse background knowledge and learning styles, I integrated multiple teaching methods for each laboratory session. For example, I will present a PowerPoint introduction to provide background knowledge on chosen curriculum which helps bring students to a more balanced starting point. Using the scientific method students will be presented with a problem and asked to create a testable hypothesis. From there, hands-on wet lab activities will be used which allows students to collaborate in groups and assess their hypothesis.
In order to foster the sense of small learning communities, students will work in groups and then gather as a class at the end of the period to share what each group found and how that relates to each other’s results. This allows students to discuss their own conclusions with each other and learn from each other’s discoveries.
All of these strategies will help implement inquiry-based learning as students collaborate during activities to understand the material, are required to think more deeply and hypothesize about an outcome, and can relate the lesson back to real-life (as we discuss how studying DNA can lead to disease identification or crimes).
3D: Evaluation of student understanding In order to assess how effective these teaching methods are, students are presented with both a pre- and post-test consisting of curriculum-based questions. To match the individual pre-/post- test answers the students were asked to create a specific code. Students were also asked to mark their gender. The questions were designed as short answer, which causes the student to use applied knowledge (rather than solely memorization) to answer. The following questions were used for assessment:
Draw the shape of a DNA molecule. What is the structure called?
Please list the four nucleotides and how they match to make up DNA. Why is it important that they match together in a certain way?
Why is it important to study DNA in the lab? Can you give a specific example?
Below is a picture of a gel with two DNA samples that have been run through it. Label which band is the larger piece of DNA and which one is the smaller piece. Why are they at different places on the gel??
Students were also asked to rate their interest in genetics on a scale of 1-10 with 1 being no interest and 10 being very interested.
A rubric was then created to assess student answers to each question. The following was used to assess answers.