The Jedi 'mind trick' is implied to only work on those with weak minds at numerous points in the series. The trick has been shown to work on stormtroopers in A New Hope.
Is the "weak mind" of stormtroopers due to them being clones of Jango Fett or a result of their genetic manipulation/upbringing? Did pre-stormtrooper "Clone Troopers" have this weak mind as well?
We don't know if those stormtroopers are Jango Fett clones, but if they are, the clones had their mind tampered to make them more docile. From the Attack of the Clones script.
LAMA SU: You'll find they are totally obedient, taking any order without question. We modified their genetic structure to make them less independent than the original host.
This tampering may explain why they are affected by the mind trick as they have less willpower to resist.
But also note that all soldiers, clone or not, are used to obeying orders. I think this makes them vulnerable to such suggestion.
In addition to what DavRob said, the Fett model clones were NO LONGER the main complement of Stormtroopers by 0 ABY (aka the year A New Hope happened).
From Wookieepedia:
... Thus, the Fett clones were ironically reduced to a minority status after years of virtually filling the stormtrooper ranks in its entirety. According to a stormtrooper's entry log in the 501st Journal, none of the Fett clones were ever truly able to come to terms with serving alongside recruits and different clones, all of whom were disdainfully dubbed as the "new guys."
Commander Cody, a first generation clone of Jango Fett and a veteran of the Clone Wars, found stormtrooper recruits to be absolutely intolerable. Due to the significant decrease in the Imperial Military's operational effectiveness and his own feelings of nostalgia over the Republic's "army of one man," Cody viewed enlisted troopers as incompetent idiots, all of whom he would have gladly sacrificed for just one real clone trooper. (src: The Force Unleashed 2)
Please note that, leaving this aside, the troopers that Obi-Wan "hand"-winked into thinking these were not the droids they were looking for were some sort of random patrol from a garrison on backwater, a$$hole-of-the-universe planet. For some reason, I have a feeling they were kind of the worst of the worst - sort of "If you tick off the officer you'll be serving the rest of the term on North PoleTatooine garrison".
Jango's mind was probably naturally bright, but also sharpened by experience. Clones were basically blank slates, and with their aging so prematurely, had weaker minds However, they were cloned, and cloned to take orders "without question", hence their easy to control minds.
Resistance to mind trick is not genetic thing, you can see phrase like "I am trained to resist it" many times in the Universe.
