In this video module, students learn how scientists use genetic information from dogs to find out which gene (out of all 20,000 dog genes) is associated with any specific trait or disease of interest. This method involves comparing hundreds of dogs with the trait to hundreds of dogs not displaying the trait, and examining which position on the dog DNA is correlated with the trait (i.e. has one DNA sequence in dogs with the trait but another DNA sequence in dogs not displaying the trait). Students will also learn something about the history of dog breeds and how this history helps us find genes. The methods shown are the same as those used in studies looking for genes in people for diseases like cancer, diabetes, and heart disease. This lesson will take one full class period. In preparation for the lesson, it may be helpful for students to have some basic understanding of what DNA is and that differences in DNA between people can cause genetic disorders. However, these topics are reviewed briefly in the lesson. All necessary handouts and worksheets are downloadable in Word and PDF formats, and students need only paper and pen/pencil to complete the lesson. Other than a few group discussion questions, there are four main in-class activities in this lesson. First, students match 4 dog breeds to 4 breed behaviors. Second, students make a dog breed by choosing founders from 28 dogs. Third, students complete a chart showing 3 DNA positions in 8 dogs to demonstrate understanding of what it means for a site on the DNA to be correlated with a specific trait. Fourth, students use real DNA data from a specific scientific study to find the gene that is altered in boxer dogs displaying the trait of white coat color.