Transgenic mice are laboratory mice that have been genetically modified to carry genes from other species. This is done using techniques such as gene transfer, allowing researchers to study the effects of specific genes on development, behavior, and disease. These mice serve as valuable models for understanding human diseases, including cancer and diabetes. The creation of transgenic mice involves inserting a desired gene into the mouse genome, which can then be passed on to future generations. This process helps scientists investigate gene function and interactions, contributing to advancements in biomedical research and the development of new therapies.