To complement AbleWeb BRCA1 activity

Most molecular biology and biological sciences students understand that the polymerase chain reaction (PCR) is used to amplify DNA. However, we have found that some students experience conceptual misunderstandings, a lack of detailed comprehension of the PCR process, or difficulties with troubleshooting and predicting the effects of alterations to the standard PCR process. We hypothesized that a problem-based learning approach that incorporates a kinesthetic modeling of the PCR process could address these problems. During this hands-on learning activity, students “amplified” a specific region of template DNA through three cycles of PCR using a “toolkit” composed of a) intertwined, supercoiled, and double-stranded yarn representing template DNA, b) short wax sticks representing primers, and c) long wax sticks representing the PCR products. Instructors can introduce a variety of assessments, including real-time image capture of the models, pre- and post-activity assessment quizzes, and homework assignment to gauge student learning. We administered identical four-question quizzes worth 12 points to 28 undergraduate students before and after the activity. The mean score on the post-quiz was three points higher than the pre-quiz score, demonstrating a 75% increase in score. Moreover, we found that students who began the activity with lower levels of understanding experienced the most significant learning gains. This hands-on, student-centered, kinesthetic activity allowed students to (i) visualize PCR processes, (ii) construct a model of the PCR process, (iii) correct common misconceptions and sources of confusion, and (iv) actively engage in the learning process.

Although genetics is an invaluable part of the undergraduate biology curriculum, it can be intimidating to students as well as instructors: Students must reduce their reliance on memorization and dive deep into quantitative analysis, and instructors must make a long, rich history of genetics experiments clear, coherent, and relevant for students. Our Lesson addresses these challenges by having students map an unknown mutation to its gene using a modern suite of genetic tools. Students receive a Drosophila melanogaster strain with a mutation that causes the normally flat wing to bend at distinct sites along its length. Although we recently mapped this mutation to its gene, here we have renamed it "crumpled wing" (cw), an example of a pseudonym that you could use in the classroom. Like many standard "fly labs" that are taught at undergraduate institutions, this Lesson reinforces classic genetics concepts: students selectively mate fly strains to determine mode of inheritance, test Mendel's Laws, and three-point map an unknown mutation relative to known markers. But here, we expand on this tradition to simulate a more modern primary research experience: we greatly increase mapping resolution with molecularly-defined transgene insertions, deletions, and duplications; then cross-examine our data with key bioinformatic resources to identify a short-list of candidate cw genes. After extensive data interpretation and integration, students have been able to map cw to a single gene. This Lesson has a flexible design to accommodate a wide range of course structures, staffing, budgets, facilities, and student experience levels.

Some concepts in genetics, such as genetic screens, are complex for students to visualize in a classroom and can be cumbersome to undertake in the laboratory. Typically, very large populations are needed, which can be addressed by using micro-organisms. However, students can struggle with phenotyping microbes. For macroscopic organisms, the number of offspring produced, and the generation time can be challenging. I developed this lesson as a small-scale genetic screen of Fast Plants^®. These plants are amenable to teaching labs as they have simple growth requirements, a short generation time, and produce numerous seeds that can be stored for years. Seeds used for this screen are purchased pre-treated with a DNA damaging agent, removing the need for in-house use of mutagens. Also, students can screen the phenotypes without specialized equipment. The initial lesson begins with an examination of the first generation of plants. Later their offspring are screened for altered phenotypes. Students responded well to having full-grown plants available on the first day of the lab project. This lesson fostered student collaboration, as they worked with class datasets. Differences in growth due to mutagenesis treatment in the first generation were clear to students who had not worked with plants before. Identifying plants with altered phenotypes in the next generation was more of a challenge. This lesson incorporates key concepts such as somatic and germline mutations, the impact of such mutations on phenotype, and the inheritance of mutation alleles, and provides a hands-on way to illustrate these concepts.

Primary Image: Fast Plant^® phenotype differences observed in the M2 generation. This pot contains three full-sibling M2 seedlings from a single M1 parent plant. The seed of their parent plant received 50 Krads of radiation. Plants 1 and 2 are of standard height, while plant 3 is greatly elongated. Image by AL Klocko.