Bacteriophage vectors, Biology

Bacteriophage Vectors

Bacteriophages are viruses that attack bacteria. Mainly phage lyses the bacterial cells they infect (lytic phages). But many others may choose to follow either lysogenic or a lytic cycle; in the second situation, the phage chromosome integrates into the bacterial chromosome and multiplies with the latter as prophage (temperate or lysogenic phages). The prophage can dissociate from the bacterial chromosome and follow the lytic cycle.
Many  bacteriophage are used as cloning vectors, the most generally used E. coli phages being λ (lambda) and M13 phages. Plasmid vectors have to be introduced into bacterial cells which are then cloned and choose for the recovery of recombinant vectors. In contrast, the phage vectors are sprightly tested to an suitable bacterial lawn (a constant bacterial-free zone in the bacterial lawn). Phage vectors show  two advantages over plasmid vectors. (1) it is easier to screen a large number of phage plaques than bacterial colonies for the identification of recombinant vectors.(2) They are more efficient than plasmids for cloning of large DNA fragments; the largest cloned insert size in a λ vector is just over 24 kb, while that for plasmid vectors it is less than 15 kb λ Phage Vectors

The λ genome (total 48,502 bp) contains an source of replication; genes for head and tail  enzymes and proteins for DNA replication lysogeny and lysis; and single-stranded protruding cohesive ends of 12 bases (5' GGGCGGCGACCT; the other end is opposite to it; i.e.CCCGCCGCTGGA 5'). The λ genome remains linear in the phage head, but within E. coli cells the two cohesive ends anneal to make a circular molecule essential for replication. The sealed cohesive ends are known cos sites that  are the sites of cleavage during and are essential for packaging of the mature phage DNA into phage heads. The λ DNA need to be larger than 38 kb and smaller than 52 kbto be packaged into phage particles. The genes for lysogeny are situated in the segment among 20 and 38 kb; the complete or a part of this segment is deleted to create λ vectors to (1) accommodate larger DNA inserts and (2) to ensure that the recombinant phage is always lytic.

Posted Date: 10/2/2012 1:23:55 AM | Location : United States

Related Discussions:- Bacteriophage vectors, Assignment Help, Ask Question on Bacteriophage vectors, Get Answer, Expert's Help, Bacteriophage vectors Discussions

Write discussion on Bacteriophage vectors
Your posts are moderated
Related Questions

Structure of HIV HIV is a spherical enveloped virus of about 90-120 nm diameter .In nucleocapsid is icosahedral. Its genome consists of a single stranded RNA filament segmented

Encystment – Protozoan Encystment is characteristic of the life cycle of many protozoan. The protozoan secretes a thickened envelope (cyst) around itself and becomes inactive

List the four basic points to be kept in mind when advising food exchange. To develop the food exchange list points to keep in mind are: a) Group similar foods in one group.

how does these phylem parasites????

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Explain Procedure for Detection of Metanil Yellow? Carry out the exercise following the steps enumerated herewith. 1. Suspend the food sample in water and shake vigorously.

Q. Explain causes of Shigellosis? Shigellosis is caused by the genus Shigella and is a common enteric (intestinal) infection. The genus has four serological groups,

Explain the Energy requirement in Postoperative Nutritional Care? Adequate calorie intake is critical for successful outcome of surgery and should be provided in the form of ca

Given an individual who is heterozygous at 6 loci, how many different gametic Genotypes are possible? A. 36 B. 12 C. 32 D. 48 E. 64