You have isolated a mutant of Shigella dysenteriae bacteria that is resistant to kanamycin, and you want to find out what gene is responsible. Design a protocol using genetic selection to identify it

It is possible to identify the function of a gene by site-specific targeted mutagenesis (i.e., by using a reverse genetics approach).  

Explanation:

Targeted mutagenesis is an approach widely used in molecular biology in order to determine the functions of endogenous genes. Targeted mutagenesis is a type of genetic technique known as reverse genetics since it is a technology that enables to identify the function of a gene by modifying its product (i.e., its corresponding messenger RNA), thereby synthesizing non-functional proteins.

Moreover, it is also possible to identify the function of a gene by altering its expression, for example, by using small interfering RNAs (siRNAs) that inhibit protein translation through RNA interference (RNAi) mechanisms.