Transgenic mice are laboratory mice that have been genetically modified to carry genes from other species. This is achieved through techniques such as gene insertion, where specific genes are introduced into the mouse genome. These modifications allow researchers to study gene function, disease mechanisms, and the effects of specific genes on development and behavior. These mice are valuable tools in biomedical research, particularly in fields like genetics, pharmacology, and cancer research. By observing how transgenic mice respond to treatments or develop diseases, scientists can gain insights that may lead to new therapies for humans.