Lesson 8

Nucleic Acid Structure and Function: Working with Models (Day 1 of 5)

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Objective

SWBAT identify the components of DNA and investigate the process of DNA replication using paper, puzzle piece, and 3-D DNA models

Big Idea

Get your students communicating their knowledge of DNA structure and function through their analysis of a variety of DNA models!

Notes for the Teacher

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.9-10.1SL.9-10.1SL.9-10.1dRST.9-10.1RST.9-10.4SP2SP7SP8XC-SF-HS-2

On Day 2, we utilize 3D models of DNA for comparison and deeper discussion.  Standards:  W.9-10.1SL.9-10.1SL.9-10.1dRST.9-10.1RST.9-10.4SP2SP7SP8XC-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.9-10.1SL.9-10.1SL.9-10.1dRST.9-10.1RST.9-10.4SP2SP7SP8XC-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.9-10.1SL.9-10.1SL.9-10.1dRST.9-10.1RST.9-10.4SP2SP7SP8XC-P-HS-1XC-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.  Here is the funding information associated with the creation of these models:                 

  • 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!  

The Classroom Flow: Introducing the Activity

15 minutes

1.  Start out the lesson by asking students to discuss in their lab groups the following prompt:

What is the structure of DNA:  What does it look like?  What are its components (parts)?

2. Using the spokesperson protocol, allow students to share out their group responses and note any vocabulary they use on the board.

3.  After you collect student words, begin to add any ones missing from the structure of DNA board list.  My list of essential words includes DNA, nucleotide, hydrogen bonds, covalent bonds, phosphate group, deoxyribose, nitrogenous bases, A, T, C, and G, purines, pyrimidines.

4.  Tell students that today they will begin to explore the structure and function of DNA.  

The Classroom Flow: Working with the Paper Model

25 minutes

1.  Ask student groups to move to their lab tables.  

2.  Pass out a copy of the DNA paper model document they will be using as they look at their models.

3.  Tell them that their job is to look at each part of the paper model and attempt to identify it based upon our list of vocabulary words on the board.

4.  Remind students that today is about the conversation more than the writing and that they will be given time for that throughout the week.  I also put up helpful page numbers from our chapter for further assistance as students work independently.

5.  As students work in pairs, go around to listen in and discuss potential hints for them when they are stuck such as:  what is the general shape of a sugar?  how many carbons make up a pentose sugar?  what do all bases contain? I find that this base pairs green board image assists them as they determine the make up of bases (purines vs. pyrimidines) and I often use it as I go from group to group.

6.  As I look at the student work sample, I can see that students are understanding the basics of how to translate our terminology into the model, with the exception of the individual base names.  This will be something to look at again tomorrow after students work with the 3D model and compare/contrast the information available on each.  By the end of the day tomorrow, this sticking point should be resolved for all students. 

The Classroom Flow: Clarifying Questions and Wrapping Up

10 minutes

The two vocabulary blocks will be the concepts of pyrimidines vs. purines and determining where the covalent bonds and the hydrogen bonds are on the models/how they are represented.  

1.  Check in with students about the concept of pyrimidines and purines.  I help them remember that purines have two rings to match the two syllables in that word and that pyrimidines each have one ring and that the y in pyrimidines matches the y's found in thymine and cytosine (this helps them a lot!).  

2.  Ask students the following question:

Which bonds are easier to break: hydrogen or covalent?  

Most if not all will remember that hydrogen bonds are easier to break.  Then draw two lines on the board : a dotted line and a straight line.  Ask them which one they think represents something easier to break.  At that point you will hear "ohs!" around the room and from there almost every student will be able to make the connection and locate them on the model. Ask students to check in with each other at their lab tables with their models to confirm that they have correctly identified the hydrogen and covalent bonds on the model and what DNA components they are found between.

Students should be able to tell each other and you the following:

  • Straight lines are covalent bonds while dotted/dash lines are the hydrogen bonds.
  • Covalent bonds are found between the deoxyribose and phosphate groups along the backbone of the DNA molecule.
  • The hydrogen bonds are found between the base pairs located down the middle 'rungs' of the DNA twisted ladder (double helix).

3.  Tell students that you will continue to work with your vocabulary words and the models tomorrow. 

Now on to Day 2!