真核生物mRNA的修饰加工 和奏 Ovalbumin gene 7,700bp 1 2 34 56 DNA A B CD E F G Transcription and 5'capping Extra RNA 12 3 5 6 Primary E F G transeript Cap Splicing,cleavage, and polyadenylation Seven introns Extra RNA L123456 Mature mRNA AAA(A) 1,872 nucleotides真核生物mRNA的修饰加工