I'm having trouble understanding just what you are trying to say. The note that determines whether a chord is major or minor is the 3rd, not the 7th. The majority of chords do not even have a 7th, but only a root, a 3rd and a 5th. Also scales are determined to be major or minor by the 3rd degree of the scale. Minor scales can have the 7th (as well as the 6th) either altered or not, but they are still minor based on the 3rd degree. There are 3 different types of minor scale: natural, harmonic and melodic. In the natural minor, the 3rd, 6th and 7th are lowered a half step from the major. In the harmonic minor, the 3rd and 6th are lowered, but the 7th is not. In the melodic minor, the 3rd is always lowered, but the 6th and 7th are only lowered when the melodic line is descending; when ascending the 6th and 7th are the same as in the major. But all of them always have the 3rd lowered.