OHOH pre-rRNA Box D UCUUGAACUGAUAGAN U20 SnoRNA SnoRNA U GUCG PACUUG
Nucleus transcription Nucleolus Pre-rRNP Proteins 32S 5-10 min 月 45s pre-rRNA 28s 20s 18s cytoplasm 18s 60s ribosomal ribosome
a bcd efgh ijk/ mop...sss.rrr.sss 1024 strands (b) Nucleolus (c) del of DNA amplification to produce stained polytene X chromosome as it appears in the nes. (a) Sequences along the left arm of microscope. The banding pattern results from reprod
表3-1非洲爪蟾卵母细胞rDNA扩增 细胞类型 核DNA rDNA/核 rDNA数目 核仁数目 Pg (pg) 体细胞 0.012 900 卵母细胞 37 25 2×10 1000~1500 (扩增后)
A 转录方向 ? 终止位点 B 启动子 DNA 18s 5.8S 28S 非转录间隔转录间隔 转录间隔 非转录间隔 图8-28rRNA基因串联重复排列,为非转录间隔所分开(引自 De robertis