DNA Extraction Lab (Day #1 of 2)
Lesson 1 of 10
Objective: Students will create and carry out a plan to extract DNA from human saliva (i.e. cheek cells).
Note: I recommend that you first check out this resource in order to get the most out of this lesson!
In high school I took several drafting classes and, for a while, I had hoped to become an architect. With respect to planning instruction and teaching, I feel that I can still live out the detailed approach to building something intricate and complex even though the product is a lesson rather than a certain "built environment".
The lesson-planning document that I uploaded to this section is a comprehensive overview of how I approach lesson planning. This template includes the "Big Three" aspects of the NGSS standards: Disciplinary Core Ideas, Crosscutting Concepts, and Science Practices. Of course, there are many other worthy learning goals, skills, instructional strategies, and assessments that can be integrated into a class session. I don't feel compelled to check every box but, rather, use it as a guide to consider various options and tailor the lesson in light of these.
With regard to this particular lesson...
- Students will know that all cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells. (Emphasis) HS-LS-1 & LS3-1
- Students will begin to consider the chemical basis of the Unit’s Essential Question: “What influences your identity and how does it change throughout its lifetime?”
- Students will understand that the scale at which DNA works is too small to directly manipulate however it can be observed experimentally.
I hope you get some value from my work! Please find the more intricate details of this lesson plan there.
"Turn and Talk": Divide participants into pairs that will discuss the concept together. This can be a quick way to have students share their understanding of the topic and can lead to a larger discussion. In this case, students are to share what they know about the DNA molecule, for example: its shape, size, color, and where it can be found as starters.
Teaching Challenge #1: How do I develop routines and procedures to support students to work independently in the science classroom?
Teaching Challenge #2: How can I develop a classroom culture that encourages student engagement, curiosity, and a desire to understand the world through scientific exploration?
These two interrelated challenges may not be entirely solved or conquered by this activity, however this activity represents several steps along the year-long journey (over which I get to accompany the student) and extending beyond my class. I hope that these experiences build toward a larger sense of independence and curiosity as they become adults.
Rather than starting from scratch, which would only lead to a number of dumbfounded looks and an awkward silence among the class, I direct students to use the DNA Extraction Lab Tempate and link provided. With this bit of scaffolding, students will study the protocol (per the online resource provided) and discuss the process in their teams. In other words, "what will it require for them to actually do this when they are green-lighted to go?"
In my mind I envision them as paratroopers waiting at the doorway of the C-17 cargo plane waiting for that "green light" that triggers the inevitable fight or flight response. I hope that today's prep will lead them to be eager to take the leap tomorrow rather than scurry as far away from the door as possible! This concept of a lab template is pretty standard in my classroom and can be explored a bit more from one of my previous lessons.
Next, students will agree to the specific steps that each member will perform for a fair and balanced team performance (on Day #2). They will then write up a protocol (based on the web link) that focuses on specific steps and the students in the team that will perform those steps.
Check-Off: What I try to foresee and prevent is the epic fail that can sometimes result from poor planning and communication among the team. Let's be honest, even the most well-prepared, experienced, and equipped researchers experience failure. Out of this can come some of the most interesting and unexpected discoveries but in this case I like to be the backstop so that the passed ball won't go out of bounds (sorry about the analogy if you aren't a baseball person).
From the beginning of the school year I emphasize the theme of "Investigate-Communicate-Create" as the three-pronged summary of what class is about. Therefore if proper steps are taken then there will be something interesting to communicate at the end of the experiment!
All student teams must gain approval of their designs by the me prior to starting their lab the following day. As a matter of efficiency, I group my class into eight teams of no more than four students. The expectation is that all members are completing their procedures together therefore I randomly spot check one member's work and look most closely at the protocol. Are the steps specifically written and tagged to a specific individual?
In the event that I am not buying their plan, they will need to regroup and try again. Sometimes this means that the revision process is happening while other teams are doing the lab. This can be stressful for them since the clock is ticking but it is an accountability measure so that lab is not needlessly chaotic because certain students don't know the plan or their role in it.
"Rubber meets the road": How does this look in class? Well, I want students to clearly articulate their Question; Materials; Procedures. These can be simply read and paraphrased from the companion website referred to in the lab. More specifically, what I want is for the steps to be succinctly, completely, and equitably written and each member's name must be attached to the tasks. There is no room for dead weight! A team should not be dragging dead bodies! If these design sections are not completed to my satisfaction then I send the team back to re-do the experimental design.
Please check out these two student samples!
(Extend to Day #2)