Recombinant DNA technology

Recombinant DNA technology. Hi Online Free life science study material. Plasmid: Plasmid circular DNA molecule present in procaryoytes.It is independant of main bacterial DNA. It is often used as selectable marker. It has one origin of replication sequence which makes it independent of main DNA. It has RP4 which carries gene for ampicillin, tetracyclin and kanamycin resistance. Size can vary from 1 kb to 250 kb. 10kb or less are used for cloning. Number can vary from 1-2 per cell (stringent plasmid) or 50 or more (relaxed plasmid)

Some plasmid carry tra gene which makes them conjugative plasmid. The bacteria having conjugative plasmid becomes conjugative. 5 Types of plasmid: 1. F or fertility: tra gene present. conjugal transfer of plasmid takes place in these. 2. R or resistance: Ampicillin, chloramphenicol etc resistance gene present. Makes bacterial cell resistant to the antibiotics. eg. RP4 3. Col plasmid: col gene for colicine is present. This protein kills other bacteria.eg colE1 of E.coli. 4. Degradative: this plasmid allows metabolism of unusual compound such as toluene, salicylic acid etc. eg. TUL plasmid of Pseudomonas putida. 5. Virulence: Vir gene is present (described in earlier blog). eg.Ti plasmid of Agrobacterium tumifaciens. M13 It is circular and entirely single stranded. It has 3 gene coding for capsid. It enters through pilus. It gets double stranded inside host. It does not integrate in host genome.Each daughter cell receives copy of M13 which replicate in them also. M13 vector is used in "Phage display". It is a technique for identifying pairs of genes whose protein product interact with each other. Free life science studymaterial.