Draw students' attention to the key ideas by using posters or overhead transparencies.
Begin this section with a review of DNA and protein that make up chromosomes.
Introduce DNA by having the students do Activity 3-1: Precipitation and Spooling of DNA. Follow this Activity with Activity 3 -2: Removing DNA from Thymus Cells.
Complete Activity 3-3: Building and Using a DNA Model.
Have the students use their completed DNA model to explain replication.
Review the big ideas of this section by discussing student answers to the Review Questions.
Select appropriate Projects if time permits.
At the end of the section refocus students' attention on the key ideas.
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Why do we use models of structures, such as a model of DNA, in science?