If G is "I", the "V" is D
If D is "I", A is the "V"
The exercise below is useful when you are playing a lick in G.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi6XJy3QlaoX6zjaZ_prqXMHW8aiCmxWcTcyd5YR1sUdElz6ghbGhGcB7DLRma5RlTiRZKkjSQqb1BU9_kf4ikfXcjYhacXwXgYgwu7Wb7tart8F6TcxnMm4DjZo1-ZDw_gDJQI5w/s400/5th.jpg)
All the notes are from the G major scale.
From the G on the 3rd fret of the E string to the G on the 12th fret of the G string.
Try this out and play some variation.
Cheers