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本课程“克隆载体概念与基因工程”主要介绍了克隆载体的基本概念、种类及其应用。 **核心内容包括：** * **质粒 (Plasmids)**： * 定义：细菌中存在的，染色体外的，双链，环状，能自我复制的DNA分子。 * 特点：数量（低拷贝/高拷贝），大小（1-500 kb），占细菌总DNA的比例（0.5-5.0%）。 * 质粒载体的特点：包含复制起点（ori），选择标记（如抗生素抗性、蓝白筛选），小尺寸，多克隆位点（MCS），易于从宿主细胞中分离。 * 常见质粒载体示例：pBR322，pUC 18/19。 * pBR322：由Boliver和Rodriguez于1977年开发的最早的载体之一。 * 质粒的应用。 * **其他克隆载体类型**: * 噬菌体 (Bacteriophages) * 粘粒 (Cosmids) * 噬粒 (Phasmids) * λ（Lambda）噬菌体 * 细菌人工染色体 (Bacterial Artificial Chromosome, BAC) * **不同类型的质粒**: * F质粒 (Fertility plasmids) * R质粒 (Resistance plasmids) * Col质粒 (Col-plasmids) * 降解质粒 (Degradative plasmids)：帮助宿主细菌消化天然环境中不常见的化合物（如樟脑、二甲苯、甲苯、水杨酸），含有降解特定化合物的酶基因，且通常是接合性的。 * 毒力质粒 (Virulence plasmids)：使细菌成为病原体，易于传播和复制，例如导致严重腹泻和呕吐的某些大肠杆菌（*Escherichia coli*）菌株，以及伤寒沙门氏菌（*Salmonella enterica*）。 * 接合性质粒 (Conjugative plasmids) * 非接合性质粒 (Non-Conjugative plasmids) * 严格型质粒 (Stringent plasmids) * 松弛型质粒 (Relaxed plasmids) 课程系统地介绍了质粒作为早期和广泛使用的克隆载体的优势，并拓展到其他多种类型的克隆载体，以及各种质粒在细菌生物学和致病性中的作用。
Plasmids are extrachromosomal, double standard, circular, self-replicating DNA molecules. Almost all the bacteria have plasmids containing a low copy number (1-4 per cell) or a high copy number (10-100 per cell). The size of plasmids varies from 1 to 500 kb. Usually, plasmids contribute to about 0.5 to 5.0% of the total DNA of bacteria.Example:Streptomyces sp.A plasmid is a naturally occurring extrachromosomal double stranded DNA, circular DNA.It replicates autonomously within bacterial cell.Plasmid carries an origin of replication.Plasmid vectors are the simplest cloning vectors.It is most widely used for gene cloning.Characteristics of Plasmid vector:It contains an origin of replication.It also Contain selective marker such as antibiotic resistance, blue white screening).Small in size (1.0 to 250kb)Contains multiple cloning site.Easily isolated from the host cell.Examples of plasmid vectors are:pBR322pUC 18/19pBR322 vectorIt is one of the first vectors to be developed by Boliver and Rodriguez in 1977.in this concept following details will be covered.Types of cloning vectors, plasmids, Bacteriophages, cosmids, phasmids, lamdaDifferent types of plasmidsFertility plasmidsResistance plasmidsCol plasmidsDegradative plasmidsVirulence plasmidsConjugative plasmidsNon Conjugative plasmidsStringent plasmidsRelaxed plasmidspbr322puc19Plasmid applicationsapplications of Bacteriophagestypes of vectors:PLASMIDSBACTERIOPHAGESCOSMIDSBacterial artificial chromosomeDegradative PlasmidsDegradative plasmids help the host bacterium to digest compounds that are not commonly found in nature, such as camphor, xylene, toluene, and salicylic acid. These plasmids contain genes for special enzymes that break down specific compounds. Degradative plasmids are conjugative.Virulence PlasmidsWhen a virulence plasmid is inside a bacterium, it turns that bacterium into a pathogen, which is an agent of disease. Bacteria that cause disease can be easily spread and replicated among affected individuals. The bacterium Escherichia coli (E. coli) has several virulence plasmids. E. coli is found naturally in the human gut and in other animals, but certain strains of E. coli can cause severe diarrhea and vomiting. Salmonella enterica is another bacterium that contains virulence plasmids.
