I've been messing around with my old Silver version with a Gameshark lately, and was wondering how to make Shiny Female Pokemon (The only code I could find was designed to only return male Pokemon). I was aware that IVs were used to determine both Shininess and Gender in GSC, so I looked up how exactly IVs decided these characteristics. I eventually found the data as I was looking for on Bulbapedia
(much of this information can be found in the Shiny thread at the top of this page). On looking over this data, I noticed that Pokemon whose genders are 7 males to 1 female (starters and other Pokemon that are 'gifted' to the player, so that breeding is more complicated), would require an Attack IV of 0 or 1. However, for a Pokemon to be Shiny in GSC, its IV's must all be 10s with the exception of attack which must have its second to last digit in its binary representation be 1, which means that the lowest value the Attack IV can be is 2. Thus, it would seem that regardless of the situation, a Female with a species gender ratio of 7 to 1 cannot be shiny in GSC.
Am I wrong about this? It seems like it would be noted somewhere that it is impossible to obtain some of the rarest Pokemon in a game in their shiny form for one gender.