PRIMER The three-dimensional structure of nucleic acids and proteins as it pertains to the mechanisms involved in gene regulation is the major focus of this book. Therefore, the reader will encounter many 3-D structures. The first chapter of the book presents the very basic ideas behind the three-dimensional aspects of biomolecules. The first part deals with the techniques used to determine 3-D structures. The presentation is virtually for the layperson. Then the basic structural elements found in proteins are examined. Having done this, we examine a particular 3-D structure (that includes both DNA and protein) presented with different modeling. This exercise will help you to become familiar with the different ways that scientists present their 3-D structures. We use different models because one aspect of structure and function can be better represented with one model, whereas another aspect is more suited to a different model.