Note: this is transGENIC not transgender.
Transgenic mice are mice which have had genes inserted / deleted in their genome so that they express (or not) proteins which are thought to be important in diseases.
The older term for them was knock-out or knock-in (genes deleted or introduced).
They have been around since the 1970s and are important in cancer and medicine research.
https://www.genome.gov/about-genomics/fact-sheets/Knockout-Mice-Fact-Sheet
The senator is displaying her total ignorance of the English language. No respect due. At all.
Thank you! I'll read about this interesting thing.
To be very honest, my dumbass would thought too that these are transgender mouses if i would heard about it somewhere without a proper explanation. And because english is not my native language as well. 