As far as I know, science has not been able to perform a brain transplant, and even if they were to be successful at transferring a brain, along with the brain stem, to another body, would it still function?

Movies have been the place where science cannot really go when it comes to these kinds of things. The thought experiment in movies was having the minds being transferred between two people and the adjustments those people have to make.

Is the mind the brain? The mind is considered to be located in the brain. But as we know, our brain and body act as one organism. So when you take the brain out of the mind, out of the body, the mind ceases to function.