Before you begin your preparation of this chapter, review Chapter 16. Chapter 16 includes a great deal of information on the specifics of DNA replication and protein synthesis. It would be good for you to know in advance how you are going to mesh these chapters. Keep in mind your course objectives.
Your first problem with Chapter 15 will be deciding how much of the material you will require your students to know. Some of this chapter (particularly the first part) will be easy for students who have had an introduction to chromosome biology. The latter part of the chapter could be confusing to students without a good background.
Even though Lewis has written Chapters 15 and 16 in a very readable and understandable way, this material could be potentially very difficult. It may be that you want your students to know the principles but not the technicalities.
You might wish to copy and distribute to your students the Overview of Chapter Objectives flowchart found at the beginning of this Instructor's Manual Chapter.
Table 15.1 includes the names of some of the people who made major contributions to our understanding of the DNA molecule. All of these scientists can be researched by your students for regular or extra credit.
Refer back to Chapter 3, page 51. Note Figure 3.31 on page 53. Correlate this material with the information in this chapter. Unless your students have had a great deal of experience with chromosomal material, they may have difficulty grasping the chemistry of the chormosome.
Many do not understand that ribose and deoxyribose are carbohydrates, just as glucose is a carbohydrate. These two have five carbons; glucose has six. Guide them to recall the definition of carbohydrate. Ask them from the sounds of the words, what they think might be the difference between ribose and deoxyribose. (See Figure 16.2.)
Many who have not had chemistry will not understand what a "phosphate" group is -- even though they have had the term several times in the last few chapters. (The major problem is that they don't understand the universality of certain terms. Rather they see these terms as separate entities, not as the same thing over and over.) Take a moment to sketch a phosphate group.
Show how the nucleotide of the chromosome is the same as the nucleotide of the energy molecule. Relate this information back to the chart found in Chapter 3 of this Instructor's Manual.
Notice below (in Hints Section III) the reference to Figure 15.10. Walk your students through this figure.
- I. Protein synthesis is mentioned at the end of this section. Protein synthesis is discussed in Chapter 16.
- II. The question is asked, "How do enzyme deficiencies produce traits?" This is a major question, the answer to which you will be working on for the next two chapters. Keep your goal in mind or you could become side-tracked.
- II.A. The Griffith experiments are classic; stress them. I suggest you discuss this great experiment with pictures in front of you. Students really are fascinated by this story, as they are by the succeeding story of identifying the transforming principle as DNA.
- II.C. Rosalind Franklin is mentioned in this section. Rosalind Franklin would have received the Nobel Prize along with Watson and Crick had it not been for her untimely death. (The Nobel Prize can only be awarded to living persons.) Some scientists today, in recognition of her work, prefer calling the Watson-Crick model the Watson-Crick-Franklin model. Franklin's story is indeed an interesting one. Perhaps some of your students -- especially the women -- would be interested in reading about her.
- III. Notice that Lewis says that enzymes are proteins. A basic rule is that all enzymes are at least part protein. Some of your students may have heard about ribozymes (discussed in Chapter 16), which are small RNA molecules that function as enzymes. A ribozyme is not a true enzyme, however, because it does not have a protein component.
- III.A. You may have to diagram the 3' and 5' concept. Draw a simple pentose and number the carbons.
Some of the students will need to be reminded that each joint represents a carbon atom. Now show them how this basic pentose fits into Figure 15.9.
- III.A. & III.B. As you work through these sections, refer back to Figure 3.31 and the information in Chapter 3 beginning on page 51.
- III.B. To work through this section, use Figure 15.10, or else use your ingenuity to make a model out of balls and string. You will have some students who need a strong visualization of this material.
Notice the introduction of the word chromatin. Consider suggesting that your students put together a chrom- list, a list of all the words past and future that include chrom-.
- IV. Before you begin this section, be certain the students understand the physical appearance of the DNA molecule. See also the notes above in the Possible Approaches to this Chapter section.
- IV.B. This section includes many new words. Consider writing out the process in simplified form, a sequence of steps to show a conceptual progression. Then, go back in and add the technical terms.
- V. Go through this with simple diagrams. Add to and expand each diagram.
