Mixolydian scale is an useful scale to use over dominant chords and in the Blues genre.
The scale degree is as followed: 1 2 3 4 5 6 b7
So if you are playing over a C7 chord, you can use the C Mixolydian scale which is also the 5th mode of the F major scale.
C Mixolydian: C D E F G A Bb
You can also play the C Mixolydian scale over C9, C11 and C13.
Try the C Mixolydian scale over a Fmaj7 chord too.
Have fun.
