There are two minor scales that I will outline, the harmonic minor scale and the melodic minor scale.
When applying the '221' convention to minor scales and the lower tetrachord is used the seventh note is sharpened.
The harmonic minor is the same ascending and descending. This is the minor that has the same notes as its Relative Major.
Cmajor - Aminor
Harmonic Aminor Scale
A, B, C, D, E, F, G, A
The melodic minor is different when it ascends to when it descends. The sixth and seventh notes are sharpened when ascending and restored when descending.
Melodic A Minor Scale (ascending)
A B C D E F# G# A
Melodic A Minor Scale (descending)
A B C D E F G A
The accidental notes that a key or mode contains can be easily worked out by looking at the Diatonic Scale Matrix .