A Fishy Way to Discuss Multiple Genes Affecting the Same Trait

Citation: Smith M ( A Fishy Way to Discuss Multiple Genes Affecting the Same Trait Michelle Smith 0 Series Editor: Cheryl A. Kerfeld, University of California Berkeley/Joint Genome Institute, United States of America 0 School of Biology and Ecology and Research in STEM Education (RiSE) Center, University of Maine , Orono, Maine , United States of America N Deduce information about genes and alleles from analysis of genetic crosses and patterns of inheritance. N Interpret complementation tests to determine whether two mutations affect the same gene, and explain the requirements and the basis for these tests. Target age group: The target age group is an undergraduate genetics course for majors, although this activity could also be part of a high school biology unit on mutations. The genetic alteration of DNA through mutations and the inheritance of mutations is part of the National Academy of Sciences Framework for K-12 Education [7]. - Many genetics classroom activities focus on inheritance patterns of a single gene with two different alleles. While valuable, these activities overlook additional areas of genetics research, such as multiple genes controlling a single trait. In this activity, students are introduced to the concept of complementation (see Box 1) and then determine whether blind cave fish from different locations have mutations in the same gene or different genes. Although this activity could be taught in many ways, here it is presented as a lecture with several clicker questions (see Box 2). Student responses are shown to help instructors gauge the range of student answers. Although there are many examples of genetics activities involving monohybrid and dihybrid crosses, it can be difficult to find activities that focus on more than one gene and a non-simple inheritance pattern. Here, I present an activity that asks students to consider whether multiple genes are responsible for blindness in the The Education Series features noteworthy, innovative open-education programs to enhance understanding of biology. Box 1. Concepts at a Glance Genetics/molecular biology leads into evolutionary biology Students learn to: I have taught this concept using a variety of active learning strategies. Here, I present the information as an interactive lecture with multiple-choice clicker questions (see Box 3), but this activity could also be taught as a small group activity, assigned as homework, or changed so students would be answering only open-response questions. The advantage of presenting the activity as a Box 3. Teaching Tools Box To help instructors present this concept in class, a PowerPoint file of the interactive lecture slides can be found in Supporting File S1. Movies about how to use clickers in the classroom and a free instructors guide to the effective use of clickers can be found at http://www.cwsei.ubc.ca/resources/ SEI_video.html. Box 4. Evaluation Tools Formative assessment questions on complementation In addition to learning about complementation in lecture, students answer homework questions. The homework assignment asks students to answer easy (Figure 7) and medium (Figure 8) questions similar to the clicker questions, but also asks them a more difficult question (Figure 9) about a complementation table where only a fraction of the complementation results are included. This problem is challenging for students because they have to decide which cross will give them new information that they cannot already acquire from the complementation table. Summative assessment of student learning Several different measures suggest students learn about complementation. First, students were given a complementation question on the exam similar to the difficult homework question (Figure 10) and 88% of the students answered correctly. Second, I gave the Genetics Concept Assessment (GCA) [11] the first day of the class and put the identical questions on the final exam. One question on this assessment asks about complementation (Figure 11). On the pretest, only 44% of the students answer this question correctly, but on the posttest 93% of the students answer this question correctly. lecture with multiple-choice clicker questions is that I can provide quantitative data about how students respond, giving instructors an idea of what fraction of students understood the concept as the class progressed. In this paper, I also include examples of homework and exam questions that ask students to further explore this concept (see Box 4). The data shown here are from a large lecture genetics course at a state university (n = 120 students). The classes met twice a week for a 90-minute lecture and also included a 50-minute recitation section. Demographic Information Class Standing 18% junior, 74% senior 62% biology, 23% biochemistry During recitation section, students worked in small groups to solve genetics problems. The course included weekly homework, clicker questions in each lecture, and three exams. Student demographic information is included in Table 1. Engagement: Introducing Complementation Using Human Deafness I begin this unit by building on two concepts we have already covered in the course: 1) identifying autosomal inheritance patterns and 2) analyzing pedigrees. Specifically, students analyze a human pedigree on the inheritance of deafness (shaded individuals) to review these concepts (Figure 1A). Human deafness is a good example for introducing students to multi-gene traits because mutations in at least 57 genes cause deafness that is not associated with any other symptoms (http://deafnessvariationdatabase.org). I ask the class to tell me about the inheritance pattern for the pedigree in Figure 1A. Students are quick to volunteer that this pedigree is more consistent with an autosomal recessive inheritance pattern. I then ask students to tell me about the inheritance pattern in the Figure 1B pedigree. Students again say that the pedigree is more consistent with an autosomal recessive inheritance pattern. Next, I tell students that a deaf person from the family in Figure 1A has a child with a deaf person from the family in Figure 1B, and that child can hear. This result is surprising because if we were considering a simple Mendelian inheritance pattern, two people who are deaf because of autosomal recessive mutations would have a 100% chance of having a deaf child. I then ask the class: how can you explain the child from the mating between the two pedigrees? Students often suggest that the sperm or egg that created the child had a spontaneous mutation that made a mutant allele normal (a possibility, but not very likely) Figure 2. A slide introducing students to the terms complementation and noncomplementation in the context of the human deafness example. doi:10.1371/journal.pbio.1001279.g002 or that the child has the genetic mutations but for some environmental reason, s/he is not deaf (another possibility, so I respond by saying let us assume all i (...truncated)