This bass line shows some of the patterns you can play over dominant 7th chords in a jazz blues progression. It's basically just outlining the triads, using an occasional passing tone and putting the 7th at the bottom - I like to do that. To make your own walking bass lines just start with the root at the beginning of each measure and then walk up or down playing the other important intervals, such as the 3rd, 5th and 7th. The chord progression is fairly common: I-IV-I-I-IV-IV-I-I-V-IV-I-V. Pardon the backing track - it's as good as I can get. I just needed to show what the chords were for this line. You can turn the backing track off if it gets to you.