Free Response Questions

Chapter 19 & 20


1. DNA isnŐt just floating around in the nucleus like long pieces of string. In order to fit into this small space it is intricately and carefully packaged. I would like you to both discuss and illustrate  how this packing is accomplished. Use your book, pages 344-346, especially figure 19.1. Be sure to include a discussion of the meaning of the following words: histones, nucleosomes, chromatin, heterochromatin, euchromatin.


2. Describe the two different kinds of non-coding repetitive DNA (Tandemly Repetitive DNA and Interspersed Repetitive DNA) and their different characteristics. Be sure to include a discussion of centromeres, telomeres, Alu elements, Fragile X syndrome, HuntingtonŐs Disease.


3. Explain how gel electrophoresis works. Be sure to explain why it is used. Explain in a stepwise process how it is done. Be sure to include a labeled illustration of the different steps. Include technical considerations since these are important. Use my lecture notes, the book (p. 374 ŇMethodsÓ and text pages 372-373), or the animation at the DNAi website which is excellent ( Find the animation by following this path: Technique->Sorting & Sequencing->Gel Electrophoresis

Another link to demonstrate gel electrophoresis can be found at:


4. Explain the polymerase chain reaction (PCR). Why is it so important? What is it used for? Be sure to explain what materials are needed to make it happen. Explain in a step by step process what happens. Be sure to include a labeled illustration of the different steps. The book does a nice overview (page 371 “Methods” and the written text 371-372). To see a great animation go to the DNA Learning Center and run the animation on “Amplification” ( Check out the “Amplification Graph” too. How long does it take to produce this many copies of a piece of DNA?

Please note: This free response (as well as #4) is critical to know well since you will probably see these questions on the AP Bio exam.


5. Discuss gene expression in eukaryotes. You will need to read the book from page 353 beginning with the section entitled, "Transcription Initiation is Controlled By Proteins That Interact with DNA and Each Other," and ending on page 356, bottom of the first column. Be sure to mention the following items:

a. The typical eukaryotic gene and how it produces and modifies its mRNA (see figure 19.8) Diagram and discuss this process (this is a review from a previous lecture with a few new details).

b. Discuss and illustrate the important points made in the CD ROM (Activity 19.1) slides 1 and 2. Relate this back to the first slide of Chapter 19 Lecture 3.

c. How transcription factors work. Specifically describe the role of activators, enhancers, promoters,terminators (see figure 19.9). See slide 4 in the CD ROM (Activity 19.1) because it animates and explains this beautifully!. Diagram and discuss this process.


 6. Discuss the details of how a human gene is ŇclonedÓ into a bacterial plasmid as is described in figure 20.3 and on pages 367-368 in your text. Be sure to describe the details of all five steps. Include an illustration along with a written answer.

See CD ROM (activity 20.1) for a great animated description of cloning.