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

Explain about the primary protein derivatives, Explain about the primary pr...

Explain about the primary protein derivatives? a) Proteins: These are the insoluble products which result from the incipient action of very dilute acids or enzymes. e.g. casein

Predict whether narrowing or widening of the blood vessels, Body temperatur...

Body temperature is homeostatic ally regulated around a set point. Given your knowledge of negative feedback and homeostatic control system, predict whether narrowing or widening o

Explain the scanning electron microscope, Explain the Scanning Electron Mic...

Explain the Scanning Electron Microscope It can be used to observe intact cells or cell components directly. Then sections are not necessary. It is used for visualizing surface

Things to do before an earthquake for minimizing losses, Things to do-  We ...

Things to do-  We ought to aide by earthquake resisting building codes during construction and retrofitting of existing buildings. We should have a first AID box handy and learn

Shapes - types of nursing units, Shapes: Nightingale Ward  In the 1...

Shapes: Nightingale Ward  In the 1940s,  this traditional nursing unit was based on  the long rectangle pavilion type ward and self-contained unit. This concept is establis

Endocrine glands - kidney, KIDNEY S - Origin . They develop from the ...

KIDNEY S - Origin . They develop from the mesoderm of the embryo. The kidneys secrete three hormones: renin, erythropoetin and calcitriol. (i) Renin . Whenever the rat

What is orthopedic, Orthopedic Prophylactic antistaphylococcal drugs ad...

Orthopedic Prophylactic antistaphylococcal drugs administered preoperatively can decrease the incidence of both early and late infection following joint replacement. They also

Explain the parental gametes and recombinant gametes, In genetic recombinat...

In genetic recombination by crossing over what is the difference between parental gametes and recombinant gametes? Parental gametes are those gametes that keep the original lin

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