Overview and Rationale


The goal of this unit is to teach students:
  • the basic functions of DNA
  • what it is
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* what it is made of
  • why it is important
  • how it replicates itself
  • how its information is used to create proteins in transcription and translation
  • what mutations of DNA look like and how they can effect its function
  • how scientists use DNA to understand disease and in identifying individuals through DNA testing

Holoweski Rationale Section

Days 1-7: We will be working with DNA models that the students construct throughout the unit. This continual revisiting of the model will show to students that this information is all related (DNA structure, replication, transcription, and translation). The information they use to construct their model on one day will build information for what is to be completed the next, thereby scaffolding their knowledge of DNA. Students can therefore more easily connect the ideas of DNA structure, replication, transcription, and translation because they will see how they all connect to the same DNA model and how to demonstrate the different functions using it.

Days 1, 2, 11, and 12: We use DNA testing to solve a mystery as a hook for students. It is a real-world example that is interesting and will resonate with student interest. Later, the other functional reasons DNA is important will become clear, but students may not be as interested in finding the structure of DNA if they are not doing it to ultimately solve a mystery.

Days 9 and 10: The BLAST activity is used as an authentic experience teaching students about mutation but also more broadly, showing students how scientists do science. The activity not only asks students to learn about mutation, it also reviews previously discussed ideas such as transcription and translation and asks students to connect the activity to other concepts they know about DNA. This activity also uses challenge questions that are designed to connect DNA technology to evolution, gene therapy and ethics. These are ripe discussion topics that hit on many of the interesting current events happening in the scientific community around DNA research.

Overall rationale:
  • We have a mixture of demonstration, inquiry and assessment lessons in this unit, mixed in for different learning styles and preferences.
  • We have made a deliberate attempt to scaffold activities to connect different parts of the unit together. For instance the lesson on transcription and translation has a homework assignment that connects to mutation, the BLAST activity connects to mutation and transcription/translation, and the DNA models are used from one day to the next to scaffold DNA structure, replication, and transcription/translation.
  • Formative assessment is used throughout the lesson in the form of worksheets and diligent observation and guided questions from the teacher
  • We spend multiple days to cover topics so students can explore concepts in multiple ways, for instance we have three different strategies for covering transcription and translation on the three days these topics are explicitly covered and we bring up these concepts throughout the lesson to deepen student understanding.
  • We have included real-world examples of how DNA is used including DNA fingerprinting, paternity tests, and the BLAST activity.

Quist Rationale Section

How did we make the topic meaningful for students?
According to the constructivist literature one of the key ways to make a topic meaningful to students is to include authentic experiences. The BLAST activity, called Connecting DNA to Disease Using BLAST, involves the students using an authentic bioinformatics tool on an authentic research problem. In addition, many of the students have watched forensics shows on television, like CSI, and have heard of DNA fingerprinting. We motivate the entire unit by explaining that DNA can be used to solve crimes, which is of interest to many students, as evidenced by the popularity of these shows.

How did you make use of inquiry?
The BLAST activity is inquirty based. The first part of the activity is a benchmark lesson, in which students learn how to use a tool for scientific investigation. The NSES list the ability to use technology and mathematics to improve investigations as fundamental for scientific inquiry. Here, students practice this skill with the tool BLAST. The next part of the activity is inquiry-based, since students have to figure out a procedure for identifying a genetic sequence themselves based on what they've learned about how to use BLAST for protein sequence in the benchmark lesson. The NSES indicate that the abilities necessary to do scientific inquiry include the ability to design and conduct a scientific investigation. In the BLAST activity, students engage in inquiry by designing the methodology themselves.

What are the ways in which you assessed student learning?
We did both formative and summative assessment. It is important to do formative assessment, because it allows the teacher to gauge student progress on learning the material. It also allows the students to gauge their own understanding of the material. For the teacher, formative assessment can result in course corrections, as the teacher speeds up or slows down to keep pace with the students. For the student, it can indicate what he or she needs to study more thoroughly. We also performed summative assessment in order to assign grades for the unit. While it is not included in the unit design, we would probably consider a follow up to the summative assessment, which allows the students to correct the material that they missed on the test.

How did you take account of students' prior experiences and knowledge?
According to constructivist teaching theory, activating prior knowledge is an important first step in teaching a lesson, since it gives the teacher a feel for the foundation on which the knowledge will be constructed. It also tells the teacher how to pace the lesson and how much to review at the outset. Throughout the Genes and DNA Unit, we activate prior knowledge at the beginning of our lessons through discussion. For example, at the beginning of the Transcription and Translation lesson we ask the students about cell division and the organization of the cell, which is prerequisite knowledge for the lesson. Since we are using the edible models throughout the first half of the unit, we can also activate the students prior experiences with the model, asking them how they'd use the edible models to represent a phenomenon before they do it. For example, during the RNA Structure lesson, we ask the students how they would apply the edible modelling methods that they used to build models of DNA to the problem of modeling RNA.

How will you sequence lessons so that they support the understanding of the learning outcomes?
If you read the lesson sequence, you will note that the majority of the lessons in our Genes and DNA Unit build directly on the material learned the day before. For example, the Transcription and Translation lesson builds on the DNA and RNA Structure lessons, which happen three and one days before respectively. The latter lessons, Connecting DNA to Disease Using BLAST and DNA Fingerprinting, do not build on the lessons immediately preceding them and instead build on the DNA Structure lesson that kicked off the unit. We place these lessons at the end, however, because they require a sophisticated understanding of DNA, which may be gained through the course of the unit. An additional advantage of the lesson sequence we have chosen is that it is consistent with the textbook. This makes it easier for students to use the textbook to supplement their understanding.

How will you help students to make sense of the materials?
According to constructivist teaching theory, students learn best the knowledge that they construct for themselves. We apply constructivist teaching methodology throughout the unit to facilitate the students making sense of the materials. Consequently, while we do use slide shows, they are used to provide representations for discussions, rather than content for lectures. In fact, most of the information is conveyed through discussions, hands-on activities, worksheets, homework, and group work, during which the student is taking a very active role. In the discussions, students are asked to make connections between the concepts they are learning in the unit. For example, in the Transcription and Translation lesson, the students are asked to explain how the Central Dogma relates to the regulation of protein expression. In group work, they are given the opportunity to bounce their ideas off of their classmates, a process which helps them refine their thinking. For example, in the Mutation lesson, they work in pairs to mutate, transcribe, and translate DNA sequences, exploring the consequences of DNA mutation at the protein sequence level. Finally, in the hands-on activities, they are asked to engage in inquiry, developing their own procedures for solving a problem. For example, in Connecting DNA to Disease Using BLAST lesson, the students are asked to develop their own procedure for identifying a genetic sequence using BLAST.

Quist and Holoweski - Genes and DNA Unit Design

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