There is a way of producing a sex-able white chick that does not involve wing feathe/vent sexing.
Unfortunately from the selection of pure breeds, which genes to breed into the sire or dam line, what to select for in each generation to create it is patented.
I shall err on the side of caution and say that you have mentioned 2 [ of several ] genes are in the sire line, and 2 [of several ] in the dam line, and they are not they same ones.