.OG-CGU AAA A G GGUAA U-A C U G rp G-C G-C A A A G C 2 G C U U A Irp\G U CA A G U G G-U U C A-U C-G A G U-A A-U C C G-C C-G C 140 A C 140 u -A C G-C uCA- UUUUUUUL… U AA UUUUUUUu. cGGG C CGGG AA A G-C C-G C C-G\ A AAAC-G-P C UU AA 1-2和34 2-3茎-环结构 茎-环结构形成 形成