Watch the Blues For Dori Solo 2 online guitar lesson by Chris Buono from Guitar Lab: Blues Soloing

About that G7, just like a 3rd bar IV chord (Basic Eight) or 2nd bar V chord (Jonesing For Trouble) is a dead giveaway for an eight bar blues, or at least a blues with an alternate bar count; so is a IV7 chord in a minor blues the telltale sign it's a Dorian blues - look for it!