2.Types of RNA RNA分子的种类 Messenger RNA,mRNA (RNA)is the direct template for protein synthesis,occupy about 5%of total cellular RNA. 是蛋白质合成的直接模板，占细胞总RNA的5%左右。 Ribosomal RNA,rRNA(核糖体RNA):is one of the main components of ribosome,occupy about 80%of total cellular RNA,also play catalysis roles during translation.是核糖体的主要组分，约占细胞总RNA的 80%左右，在翻译过程中还具有重要的催化作用。 Transfer RNA,tRNA(转移RNA):its function is to transfer specific amino acid to ribosome for the polypeptide synthesis,.occupy about 1:5%of total cellular RNA.其功能是 将特异的氨基酸运送到核糖体参与多肽合成，约占细胞总 2025/5/15 6 RNA的15%
2025/5/15 16 2. Types of RNA RNA分子的种类 Messenger RNA，mRNA（信使RNA）：is the direct template for protein synthesis, occupy about 5% of total cellular RNA. 是蛋白质合成的直接模板，占细胞总RNA的5%左右。 Ribosomal RNA，rRNA （核糖体RNA ）：is one of the main components of ribosome, occupy about 80% of total cellular RNA, also play catalysis roles during translation. 是核糖体的主要组分，约占细胞总RNA的 80%左右，在翻译过程中还具有重要的催化作用。 Transfer RNA ，tRNA（转移RNA）：its function is to transfer specific amino acid to ribosome for the polypeptide synthesis, occupy about 15% of total cellular RNA. 其功能是 将特异的氨基酸运送到核糖体参与多肽合成，约占细胞总 RNA的15%
三、Features of RNA synthesis RNA合成的特点： 1.RNA synthesis is catalyzed by RNA polymerase, using DNA as template and following the base- pairing rules.RNA是以DNA为模板，由RNA聚 合酶以碱基互补的原则催化合成的； 2. For a specific gene,only one strand of DNA was used as the template for is RNA synthesis,i.e.the transcription is asymmetric.只有一条DNA链作为 一个基因的RNA模板，也就是说转录是不对称的； 3. Direction of RNA synthesis:5'-3' 202551RNA链由5’-3'的方向合成。 17
2025/5/15 17 三、Features of RNA synthesis RNA合成的特点： 1. RNA synthesis is catalyzed by RNA polymerase, using DNA as template and following the basepairing rules. RNA是以DNA为模板，由RNA聚 合酶以碱基互补的原则催化合成的； 2. For a specific gene, only one strand of DNA was used as the template for is RNA synthesis, i.e. the transcription is asymmetric. 只有一条DNA链作为 一个基因的RNA模板，也就是说转录是不对称的； 3. Direction of RNA synthesis: 5’- 3’ RNA链由5’- 3’的方向合成
3'end B 3'end OH OH DNA template strand Tii网 ong ●3 Strend A N业L 5'Strand B Region being transcribed 2025/5/1MR 18
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四、Basic process of transcription 转录的基本过程： Basis process of transcription including recognition of template,initiation,promoter clearance,elongation and termination,both in prokaryotes and eukaryotes.无论是原核 还是真核细胞，转录的基本过程包括：模 板识别、转录起始、通过启动子及转录的 延伸和终止。 2025/5/15 19
2025/5/15 19 四、Basic process of transcription 转录的基本过程： • Basis process of transcription including recognition of template, initiation, promoter clearance, elongation and termination, both in prokaryotes and eukaryotes. 无论是原核 还是真核细胞，转录的基本过程包括：模 板识别、转录起始、通过启动子及转录的 延伸和终止
1) Template recognition:模板识别阶段： The process that the interaction and binding of RNA polymerase with double stranded promoter DNA occurred.主要指RNA聚合酶与启动子DNA双链相互 作用并与之相结合的过程。 2)Transcription initiation:转录起始： Formation of the first nucleotide bond in the RNA. 指RNA链上第一个核苷酸键的产生。 3)Promoter clearance:通过启动子阶段： The process that the 9-mer was synthesized after 2 iation.转录起始后直到形成9个核苷酸短链的过程
2025/5/15 20 1) Template recognition: 模板识别阶段： The process that the interaction and binding of RNA polymerase with double stranded promoter DNA occurred. 主要指RNA聚合酶与启动子DNA双链相互 作用并与之相结合的过程。 3) Promoter clearance: 通过启动子阶段： The process that the 9-mer was synthesized after initiation. 转录起始后直到形成9个核苷酸短链的过程。 2) Transcription initiation: 转录起始： Formation of the first nucleotide bond in the RNA . 指RNA链上第一个核苷酸键的产生