4 Transcriptional unit of prokaryotes and eukaryotes Operon of bacteria produces polycistron mRNA Operon In a bacterial chromosome,a group of contiguous genes that have related functions are transcribed into a single mRNA molecule 在细菌中，一些功能上相关的酶的基因常一个紧接着一个 地串联排列，受同一操纵区控制，这种由多个结构基因及 其共同的转录操纵区组成的单一转录单位称为操纵子。 cistron The mRNA that encoding a specific peptide. polycistron A piece of mRNA that encoding more than one specific peptide. Most eukaryotic genes produce monocistrons
4 Transcriptional unit of prokaryotes and eukaryotes Operon of bacteria produces polycistron mRNA Operon：In a bacterial chromosome, a group of contiguous genes that have related functions are transcribed into a single mRNA molecule 在细菌中，一些功能上相关的酶的基因常一个紧接着一个 地串联排列，受同一操纵区控制，这种由多个结构基因及 其共同的转录操纵区组成的单一转录单位称为操纵子。 cistron：The mRNA that encoding a specific peptide. polycistron： A piece of mRNA that encoding more than one specific peptide. Most eukaryotic genes produce monocistrons
frp operon Promoter Promoter Genes of operon DNA trpR , tpE■trpD trpc trpB trpA Operator Regulatory RNA/ Start codon Stop codon gene polymerase mRNA mRNA 5 E D B Protein Inactive repressor Polypeptides that make up enzymes for tryptophan synthesis (a)Tryptophan absent,repressor inactive,operon on.RNA polymerase attaches to the DNA at the promoter and transcribes the operon's genes
Part 2 Structural features of viral genome 1 Introduction Each viral particle,or RNA,within a protective protein coat called capsid;or virion,consists of genetic material,DNA Grouped by nucleic acid DNA RNA viruses; Grouped by host types plant virus,animal virus and bacteria virus (phage)
Part 2 Structural features of viral genome 1 Introduction • Each viral particle, or RNA, within a protective protein coat called capsid; or virion, consists of genetic material, DNA • Grouped by host types：plant virus, animal virus and bacteria virus (phage). • Grouped by nucleic acid：DNA & RNA viruses;
病毒基因组的结构特点 ·病毒是最简单的原核生物，完 整的病毒颜粒包括外壳蛋白和 RNA coils into helix 内部的基因组DNA或RNA; ·病毒不能独立地复制，必需进 入宿主细胞中借功细胞内的一 些酶类和细胞器才能使病毒得 以复制； 烟草花叶病毒粒子，RNA外 面包围着蛋白质亚单位
病毒基因组的结构特点 • 病毒是最简单的原核生物，完 整的病毒颗粒包括外壳蛋白和 内部的基因组DNA或RNA ； • 病毒不能独立地复制，必需进 入宿主细胞中借助细胞内的一 些酶类和细胞器才能使病毒得 以复制 ； 烟草花叶病毒粒子,RNA外 面包围着蛋白质亚单位
2 Features of Viral Genome (1)Genome size of different viruses vary greatly.i.e.the DNA size of HBV is 3.2kb and encoding only 4 proteins; while the genome of vaccinia virus is as large as 300kb, encoding hundreds of proteins 不同病毒基因组差异很大 (2)A virus may employ either DNA or RNA as the genetic material,but rarely do they contain both.The genome DNA or RNA might be single stranded or double stranded.The shape might be circular or linear.i.e. X174 contains scDNA,while adenoviruses employ linear,dsDNA
2 Features of Viral Genome ▶(1) Genome size of different viruses vary greatly. i.e. the DNA size of HBV is 3.2kb and encoding only 4 proteins; while the genome of vaccinia virus is as large as 300kb, encoding hundreds of proteins； 不同病毒基因组差异很大 ▶(2) A virus may employ either DNA or RNA as the genetic material, but rarely do they contain both. The genome DNA or RNA might be single stranded or double stranded. The shape might be circular or linear. i.e. фX174 contains scDNA，while adenoviruses employ linear, dsDNA