If you are asking which method to use to check whether the gene has been knocked out or not. This can be done by using gene expression. To know which method is used to generate a knockout mouse, it is RNAi also called RNA interference. I do understand this but i am asking Gene of unknown function in the mouse genome was investigated with reverse genetic approach Knock out mouse was created was missing particular gene When phenotype of investigated mouse was compared the only difference from the wild-type was mouse kicking other mouse And I know the protein encoded was named KST So my question is what are the some of aspects of the KST protien that could be investigated in order to better understanding the biology ?