McDougal Littell Science Cells and Heredity 

Table of Contents
Page 32

Scientists use models to study cells.

Scientific Models
ScientificModel

Scientists use several different types of models.

ScientificModel

Watson and Crick used a model made from wire and tin.

Any drawing or photograph on a flat page is two-dimensional. In addition, diagrams of cells are often simplified to make them easier to understand. If you look at plant or animal cells under a microscope, you will notice some differences between real cells and the diagrams on page 22. In order to study cell structures and their functions, scientists use many types of models, including three-dimensional models. One of the most important discoveries in science involved the use of models.

DNA is the genetic material common to all cells. (You will read more about the structure and function of DNA later in this unit.) In the early 1950s, scientists had a good idea what DNA was made up of. The problem was that they could not figure out how all the pieces of the molecule fit together.

A scientist named Rosalind Franklin used xrays to produce images of DNA. The x-ray provided an important clue as to the shape of the molecule. Two other scientists, James Watson and Francis Crick, were then able to put together a three-dimensional model of DNA and present it to the world in 1953.

Today's scientists have many different tools for making models. The images at the left show a computer model of DNA along with Watson and Crick's famous model.