A researcher that uses mouse models to understand protein function in the immune system ,genetically engineered one of her mice to be missing a specific protein known as I TK.There is a special term...

A researcher that uses mouse models to understand protein function in the immune system ,genetically engineered one of her mice to be missing a specific protein known as I TK.There is a special term to describe removal of gene function to study the role of the gene.This term is ………..?