here's a more detailed breakdown of the chords in the Gmajor scale, showing the 1st, 3rd, 5th and 7th respectively:

Gmajor7 - G B D F#
Aminor7 - A C E G
Bminor7 - B D F# A
Cmajor7 - C E G B
D7 - D F# A C
Eminor7 - E G B D
F#minor7b5(or F# half diminished) F# A C E