In today's lesson, students will revise their DNA models. Then they compare their models with Watson and Crick's model. Finally, students will write a letter to the president of K'Nex encourage him to modify the DNA to better reflect Watson and Crick's model. This is a three day lesson. Day two is found at this link. Here is an overview of what students will learn today.
Since they first learned about DNA, most students have been taught that there is only one structure of DNA. To begin this lesson, have students read and summarize this handout that is based on the UCDavis BioWiki : B-Form, A-Form, Z-Form of DNA. Using three different colored highlighters, they should determine the key structural differences between the three forms. Students will also determine the role of each form of DNA.
(Note: Here is an example of one student's work.)
Using the student handout and the information from yesterday's lesson and today's reading, students will revise their original models to make them more in line with Franklin and Wilkins' data. If enough supplies are available, students should construct a new model so they can do a side by side comparison with their original model. If that is not possible, have students use parts from their original model and increase the space between nucleotides by either adding larger K'Nex pieces or by using heavy duty tape. Once students have completed their model, they should photograph it with a metric ruler in the frame for scale. They should also record the dimensions of their model on the student handout.
Students will watch the end of the movie Life Story to see the final model. (Note: In America, it can also be found under the name, The Race for the Double Helix.) (Part 1 can be found here and part 2 can be found here.)
Little Boys: 1:21:19 to 1:24:51
She Hasn't Seen It: 1:24:52 to 1:30:30
Pairing the Bases: 1:30:31-1:35:09
It's Beautiful: 1:35:55-1:41:49
While students watch the film clips, they should complete the film synopsis and evidence on the student handout.
For a shorter lesson, you may choose to watch Watson's inspirational TED talk instead.
Provide each student with the copies of the two papers published in Nature by Watson and Crick and Wilkins and Franklin. (Note: Copies of both papers can be found at a Nature Web Focus, Double Helix: 50 years of DNA. These can be downloaded as pdf copies.) Read the Watson and Crick paper as a class.
Ask the students to generate a list of new questions that scientists might have concerning DNA now that they know the structure. Students should place these questions in their lab notebooks.
As homework, students will write a letter to the president of K'Nex to encourage him to modify their DNA kit to better reflect the true size of the DNA macromolecule.