Nucleic Acid Structure and Function: Working with Models (Day 5 of 5)

This is a five day lesson series exploring the structure and function of DNA that I have been developing with my research partners at West Ed over the past three years.  By using multiple DNA models, this series gives students the opportunity for deeper exploration and discussion about the components and function of DNA as well as a chance to analyze the diverse ways each model reveals different pieces of information about DNA.  

On Day 1, we explore students' prior knowledge about DNA structure and examine paper models of DNA.  Standards: W.9-10.1, SL.9-10.1, SL.9-10.1d, RST.9-10.1, RST.9-10.4, SP2, SP7, SP8, XC-SF-HS-2

On Day 2, we utilize 3D models of DNA for comparison and deeper discussion.  Standards:  W.9-10.1, SL.9-10.1, SL.9-10.1d, RST.9-10.1, RST.9-10.4, SP2, SP7, SP8, XC-SF-HS-2

On Day 3 and Day 4, we delve into the process and scientific vocabulary of DNA replication using both paper and 3D models.  Standards:  W.9-10.1, SL.9-10.1, SL.9-10.1d, RST.9-10.1, RST.9-10.4, SP2, SP7, SP8, XC-SF-HS-2

on Day 5, we utilize puzzle piece models to compare and contrast DNA and RNA for greater depth of understanding and in preparation of for our next series of lessons on protein synthesis.  Standards:  W.9-10.1, SL.9-10.1, SL.9-10.1d, RST.9-10.1, RST.9-10.4, SP2, SP7, SP8, XC-P-HS-1, XC-SF-HS-2

I am using the models I have on hand:  a classroom model found on any science education supply website, paper models that you can build for students to use or have them build on their own, puzzle piece models I found in a closet in my classroom, and a special set of 3D printer constructed models of DNA created by researchers at Scripps Research Institute in San Diego, CA and brought to my classroom through West Ed, a nonprofit research and development agency that is also over seeing the Smarter Balanced educational testing system in many states now embracing the CCSS.  You can use any models you have on hand or others that you are able to get on loan through nearby university partners.  

My students were very happy with this lesson series and especially the amount of information they were able to understand and discuss through the focused use of these models.  I can't wait to hear about the models you choose to use and how the lesson works for you and your kids! 

Check out a note one of my students wrote to me about our time with the DNA models and what she learned from the experience.  I was so excited to see a student who didn't always feel successful in our class feel completely confident about her knowledge and to hear her contribute in both small and large discussions and activities through this lesson series using these amazing models.

My deepest appreciation to the staff at West Ed including Jodi Davenport, Matt Silberglitt, and Jacqueline Powers along with the generous project funders of the 3D DNA models used in these lessons.  

• This material is based upon work supported by the National Science Foundation under grant DRL-1108896 and by the Institute of Education Sciences, U.S. Department of Education, under grant R305A120047. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, the Institute of Education Sciences, or the U.S. Department of Education.
• For more information about the models, check out the website West Ed set up just for this project!  

1.  Ask students to recall the work we have done using our paper and 3D models of DNA.  

2.  Show them the DNA vocabulary list from the board one more time.  Use the small green board to help students visualize again the concept of purines and pyrimidines: which base is a purine/pyrimidine, how many rings they each have, and how they are bonded together into pairs.

• Note:  This review session is brief.  Students have been working diligently for four days using the models and they will be very familiar with all of the terminology you are referencing.  

3.  Using the spokesperson protocol, ask students to find one word that they need clarification on and will share with the group.  Share out and address terms as needed.

4.  Tell students that today you will be using a one last, different type of DNA model to explore DNA as well as another nucleic acid called RNA.

5.  Ask students to move to their lab tables.

• Note:  These models are ones I found in a drawer in my room and they are still available for purchase using the manufacturer information.  However, what I've found through using a variety of models throughout this lesson series is that the variety is what matters when it comes to the models we used.  Students gained a lot of analytical experience comparing models and determining what could be seen in one model that wasn't a part of another model version of DNA.

1.   Pass out the puzzle piece DNA model pieces in baggies that contain five of each type of piece to each pair of students.

2.  Give each student their DNA puzzle piece model document to help guide their discussion and review of the parts of DNA, their names, and where they are located on the model.  Remind them that the goal is to discuss their thinking and review what we have already done to learn about DNA structure, function, and replication.

• Note: This will be the third time students have used this type of document with DNA models within this lesson series, so they will be ready to get to work with very little input from you.  If you choose to use this out of sequence, please reconsider.  I tried to use this earlier on in the series last year and the extra pieces from RNA needed in order for students to determine specific bases and base pairings can be confusing.  In addition, unlike every other model we've used, the color scheme here is inconsistent:  there will be adenines in more than one color.  It is challenging to ask students to ignore color and focus on patterns while they are still navigating the novelty of DNA structure and our class protocols for using and discussing models.  I highly recommend you save this model until the end of the series for maximum impact and minimal unnecessary student frustration.

3.  Some students will immediately notice there are some pieces that they don't need in order to make a short DNA model (the ribose and uracil of RNA).  Tell them that you will be addressing those parts together as a class in the next section of the lesson.

4.  Check out the student work sample for typical student responses as they work together to put together what they know about DNA, their work with the previous paper and 3D models, and the evidence found in their puzzle piece model set.  As you can see, the writing is getting more explicit as students link their ideas about what piece represents each DNA component to the evidence from the model that supports their choices.

1.  Ask students to lay out their pieces and organize them by similarities/differences. 

2.  Give each group sticky notes so that they can attempt to name and label each of the pieces that relate to the DNA molecule.  

3. Confirm with the students that there are in fact some pieces that they have/should not have labeled and point out their shapes.  Ask students:  

What is different and similar about these two pieces in comparison to the rest

of the pieces you have labeled already?

Use the popcorn method or the spokesperson protocol to generate responses.  

Note:  Students will immediately see that two of the pieces do not have rounded edges and instead have a half moon shape.  Some students will immediately jump to identifying those two pieces as the ribose and the uracil, but most will not yet.

4.  Show students the DNA vs RNA Powerpoint presentation slides outlining the major differences between RNA and DNA.  

5.  Once you have discussed this information, ask students to work with their groups to figure out what the names of the mystery pieces are and how they fit into the model.  

6.  Circulate around the room to support students, answer clarifying questions, and pose questions  to help kids review and synthesize the information of this lesson series.  Questions you can use to support student inquiry and discovery include:

Is there any other molecule that looks or acts like deoxyribose?  (This is often enough for them to figure out the ribose piece)

• Which base is only present in DNA?  Which base is only present in RNA?  (These two questions will often get students to see that the uracil and thymine must be similar looking since they replace each other.)
• What base always goes with thymine?  (Now students will be able to connect uracil within our base pair rules/complementary base pairing and understand that whatever fits with the uracil/thymine must be adenine.)
• Of the remaining two bases, how do you know what they must be? How can you tell which base is which within this pairing? (Students will know that they have to be C and G together but they may need you to remind them about purines and pyrimidines in order to recall that the larger base of these pair has to be guanine and the smaller one has to be cytosine).

6.  Tell students that next we will be learning how DNA and RNA work together to create proteins in our bodies through a process called protein synthesis.