Genetic manipulation is a powerful tool that many researchers employ to study the effects, consequences, and cause of many biologic phenomena.  The ability to alter the genome provides levels of control that are not possible in other research techniques.  However, more often than not, it is scientifically and ethically immoral to carry out such studies in human subjects.  This is why the work of American scientist Jon Gordon in Frank Ruddle’s lab at Yale to develop the first transgenic mouse; one in which genes of another species were introduced to its genome, proved to be ground-breaking.   Due to the biological similarities between the two mammalian species, and relatively close genetic make-up, results from genetic modification in the mouse can be transferable to humans.  In the years following, significant advancements have been made to improve the techniques for genetic manipulation as well as its capacity to provide observable results.  However, it must be noted that this is not a perfect model and that any animal model will never be a perfect substitute for humans.  Additionally, the numbers of genetically modified mice used in research has consistently increased since the early 80s, which suggests a reliance on them.