基因工程chapter 05.pdf

基 因 工 程 Genetic Engineering 2013年春 主讲：仪治本 邮箱：zbyi008@126.com /genetics3 Chapter 5 Vectors Genetic Engineering 2 Chapter 5 Vectors Key points ： ①Vectors are autonomously replicating DNA molecules used to carry foreign DNA fragments. ②Vectors are based on naturally occurring DNA sequences that have been modified and combined to serve particular functions. ③Vector usages: production of single-stranded DNA, the high- level expression of protein encoding genes, and the production of RNA. Genetic Engineering 3 Essential features of vectors ： ① Be small DNA molecules, to facilitate isolation and handling. ② have an origin of replication, so that their DNA can be copied and maintained in the cell population as the host organism grows and divides. ③ have some sort of selectable marker to enable the vector to be detected. ④ have at least one, often multiple restriction endonuclease recognition site, to enable DNA to be inserted during the production of recombinants. Also called MCS (multiple cloning site). Genetic Engineering 4 Cloning vector and expression vector • A vector used for reproducing the DNA fragment is often referred to as a cloning vector. • A vector used for expressing a gene contained within the cloned DNA is called an expression vector. • All vectors are based on naturally occurring DNA sequences that can be replicated under particular circumstances. • Most commonly used vectors are based either upon plasmids or λbacteriophage. Genetic Engineering 5 1 Plasmid vectors 1-1 Plasmids