The Dorian Mode originally ascended from D to D'
Scales in Score and Tab for common Dorian Modes as gifs or pdf
Use this table to construct the mode starting on any note, using the pattern of intervals below.
This pattern of intervals: T-S-T-T-T-S-T* is the characteristic of the Dorian mode, and is a Minor scale (because of the flattened third note).
Because the mode is characterised by its interval structure, you can start on any note and progress with the same intervals to produce a Dorian mode in that 'key'.
This would be 'G Dorian':
Examples of tunes in Dorian Mode are The Star of Munster, Cooley's, Scarborough Fair, The Ships are Sailing, Pigeon on the Gate and Drunken Sailor.
* T = Whole Tone, S = Semitone