Isolation of Plasmid Dna by Alkali-Lysis Method

1. INTRODUCTION

1.1 PLASMID

Plasmids are extra chromosomal genetic material. They are rotund molecule of DNA that led an independent existence in b make uperial cell. Plasmid has cap skill of self replication or may be integrating with bacterial chromosome. Plasmid has at least one DNA sequence that can act as an origin of replication. Plasmid almost always give birth one or more gene which is responsible for a useful characteristic displayed by bacteria .e.g. Antibiotic protection gene, therefore it is used as selectable marker.

All plasmid DNA cause atleast one DNA sequence that can act as an origin of replication, so they are able to cypher with the cell quite independently of the main bacterial chromosome. The small plasmids make use of the host cells consume DNA replicative enzymes in score to make copies of themselves, whereas some of the big ones carry genes that code for special enzymes that are specific for plasmid replication.

Size and copy number of plasmid is an important possess of plasmids for cloning purpose e.g. plasmid ranging from 6-10 Kb is very satisfactory for cloning and having copy number as many as 50. Plasmid may be of following type:

F-Plasmid: having ability to promote conjugal transfer of plasmid e.g. F-Plasmid of E.



coli

R-Plasmid: responsible for providing oppositeness to host against foreign bodies such as anti bacterial resistance e.g. RP4 of Pseudomonas

Col-Plasmid: codes for colicins, protein that kills other bacteria e.g. ColE1 of E.coli and Pvocine of Pseudomonas

Degradative Plasmid: it allows the bacteria to metabolize unusual molecule such as toluene and salicylic venereal disease e.g. TOL of Pseudomonas putida

Virulence Plasmid: it confers pathogenicity on the host bacterium e.g. Plasmid of Agrobacterium.

Essential features of an ideal plasmid cloning vector

sharp size: Low molecular weight, are easier to handle, present in multiple copies, do not get damaged during isolation, surmount through cell...If you want to get a full essay, order it on our website: Ordercustompaper.com



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