Bacteriophage vectors, Biology

Assignment Help:

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.


Related Discussions:- Bacteriophage vectors

What is the significance of choanocyte, What is the significance of Choanoc...

What is the significance of Choanocyte? Unique collar-shaped cells whose flagella are responsible for generating water current in the sponge. As flagella beats, food particles

Name the disorder which is subject of ''the elephant man'', The name Joseph...

The name Joseph Merrick, subject of "The Elephant Man", is generally associated with one disorder, though it now seems likely he actually suffered from a different disorder. Name e

Carpentier-technique of operation, Carpentier: Edwards or similar annul...

Carpentier: Edwards or similar annuloplasty ring is then sutured into place by interrupted sutures to support the repair and reduce the annulus to a measured amount. The ring m

What are the nutritional components of the foods we consume, What are the n...

What are the nutritional components of the foods we consume? The foods that we consume are composed of varying quantities of the following nutritionally important components:

Molluscs., what are the economic and ecological importance of molluscs

what are the economic and ecological importance of molluscs

Rk, how many chromosomes in human

how many chromosomes in human

Can you illustrate compensation point, Q. What is compensation point? What ...

Q. What is compensation point? What is the inference of the compensation point for the plant growth? The photic compensation point is the photic energy intensity under which ae

Explain cloning vector, Cloning vector: The DNA molecule originating from ...

Cloning vector: The DNA molecule originating from the virus, a plasmid, or the cell of a higher organism into which an another DNA fragment of appropriate size can be integrated w

Antibodies, Antibodies Antibodies are important.tools for detecting and...

Antibodies Antibodies are important.tools for detecting and localising specific molecules in the cells due to their high specificity. The first requirement for this is to produ

Inter-relationships of classification, Inter-relationships of Classificatio...

Inter-relationships of Classification The aim of classification is to put together organisms on the basis of their similarities. But the question is what type of similarities?

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd