Even though the human genome was mapped over 10 years ago, scientists are still far from understanding the function of every human gene! One way to evaluate how a gene functions is to disrupt the sequence encoding it and then evaluate the impact of this change (the phenotype) on the animal’s biology. This approach is commonly used in the mouse (Mus musculus), since it shares a high degree of genetic similarity with humans. To track the animals bearing genetic changes over several generations, it is necessary to screen the DNA of each mouse in a process known as genotyping.

This video provides an overview of the theory and practice behind genotyping mice. The discussion begins with the basic principles of mouse genetics, including a review of the terms homozygote, heterozygote, wildtype, mutant, and transgenic. Next, step-by-step instructions are supplied for extracting and purifying genomic DNA from mouse tissue. Examples are provided demonstrating how to interpret genotyping results, as well as how to keep track of mice with the desired genotype. Finally, some representative applications of the genotyping procedure will be presented in order to demonstrate why this common technique is so essential to mouse research.