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

Natural vegetative propagation, in natural vegetative propagation which st...

in natural vegetative propagation which structure gives rise to new individuals?

Define features of fusarium - fungi and yeast, Define features of Fusarium ...

Define features of Fusarium - Identification of Fungi and Yeasts? Identifying features of Fusarium: 1. Wooly, white fuzzy colonies changing colour to pink, purple or yellow.

Tpes of diarrhoea, Tpes of Diarrhoea: Diarrhoea can be acute, chronicl...

Tpes of Diarrhoea: Diarrhoea can be acute, chroniclpersistent diarrhoea and dysentery.  If an episode of diarrhoea lasts less than 14 days, it is acute diarrhoea. Acute wat

Procedures adopted by numerical taxonomists, Q. Procedures Adopted by Numer...

Q. Procedures Adopted by Numerical Taxonomists? Since numerical taxonomy is an operational science, the procedure is divided into a number of repeatable steps, allowing the res

Describe pericardial rub and their characteristic, Describe Pericardial Rub...

Describe Pericardial Rub and their Characteristic ? Generation of sound: The sound is generated due to rubbing of visceral and parietal pericardial surfaces against each other

Determine the most probable mode of inheritance, In the following pedigrees...

In the following pedigrees, the disorders or traits presented follow simple patterns of Mendelian inheritance. For each trait, determine the most probable mode of inheritance, stat

Factors affecting normal blood sugar levels, Q. Factors Affecting Normal Bl...

Q. Factors Affecting Normal Blood Sugar Levels? Earlier in our discussion, we learnt that insulin is the most important factor responsible for normal blood sugar levels. Now we

What is paedomorphosis. explain in brief., What is Paedomorphosis. Explain ...

What is Paedomorphosis. Explain in brief. When sexually mature adults have characteristics which would normally be associated with the larval stage. It happens since reproducti

Explain use of repellents, Use of repellents Avoidance and early remova...

Use of repellents Avoidance and early removal of ticks are the first steps in prevention of Lyme disease. In highly endemic areas, when an engorged Ixodes scapularis tick is at

Gametes and genotypes, what type of gametes would be produced from genotype...

what type of gametes would be produced from genotype AA, Bb, AABb and someone who is heterozygous for 3 traits

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