Fig. 5. Classification of all 16 lariat-forming group II introns of barley chloroplasts according to base pairs neighbouring the determined branch-site adenosine (black circle; cf. Figure 1). Watson–Crick pairs are represented by black thick lines. Dashed black lines represent wobble or non-pairing. A consensus structure drawn from this intron set suggests weak or non-pairing upstream, with concomitant tight Watson–Crick pairing downstream of the branch-site (lower left).