The structural features of a DNA molecule are more apparent if you can look at a three-dimensional representation. Here, you can look at a 3-D view of DNA. Note: To view the molecules, you will need to install a "plug in" called CHIME.

a. How is a 3-D structure of DNA similar to the one shown in your text? How is it different?
b. Look carefully at the structures of the four bases that compose DNA. What are their structural common features? How do they differ?
c. Look again at the large DNA molecule. Can you spot the bases? How are they aligned?

In 1958, Rosalind Franklin died an untimely death of ovarian cancer at age 37. Thus, she did not live long enough to add her own account to the history that was written (and rewritten) about the discovery of DNA. Because her work was long minimized or ignored, some historians now assert that both DNA and Rosalind Franklin were discovered.

To set the record straight, several excellent biographies of Franklin are now available. You can find reviews of these books as well as other accounts of her life on the web by searching for Rosalind Franklin. What were her contributions to the structure of DNA? why was her work not given its full credit during her time? What questions would you ask her if you could interview her?

If a person must take insulin daily, how would that person know the source of the insulin? Does the source make a difference in how the insulin acts in the body? Use the resources of the web and/or consult a pharmacist to answer these questions.

In 1985, the U.S. Food and Drug Administration approved the use of BGH in cows for boosting milk production. Although regulatory agencies around the world have reached the same conclusion, the debate is far from over. Search the web for "bovine growth hormone" (or its synonyms "bovine somatotropin" or "BST") to check the current situation and report the arguments on both sides. If you can, document the situation in countries other than the United States.

In 1999, a government report asserted, "Sequence completion by the end of 2003 is a major challenge, but within reach and well worth the risks and effort." How well are we progressing to meet the goal of complete sequencing? Check one of the national web sites on the Human Genome Project to find out the current status of the project. Note also any new developments posted on the site, especially any applications to gene therapy.

Plans to develop a human cloning clinic were announced in January 1998. What are the risks and benefits associated with such a clinic? Has the clinic been completed at this time?