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

Why are grasshopper is said to show male heterogamity, a) Why are grasshopp...

a) Why are grasshopper and Drosophila said to show male heterogamity? Describe. b) Define female heterogamity with the help of an example.

In vitro studies - nutrition of embryo, In vitro Studies - Nutrition of Emb...

In vitro Studies - Nutrition of Embryo Studies involving culture of embryos excised of various stages of development (i.e., early globular proembryo, late globular proembryo o

Define endocrine or hormonal disorders - infertility, Define Endocrine or H...

Define Endocrine or Hormonal Disorders - Infertility Infertility can be caused by endocrine disorders, long-term sequelae of sexually, transmitted infections, puerperal sepsis,

Explain about the cardiovascular and circulatory system, Explain about the ...

Explain about the Cardiovascular and Circulatory System? Aging affects the cardiac muscle causing a diminished resting cardiac output. The capacity of myocardium for cellula

Concerning the body temperature how reptilia classify, Q. Concerning the ma...

Q. Concerning the maintenance of body temperature how do beings of the class Reptilia classify? Like amphibians and fishes, beings of the class Reptilia are heterothermic anima

Explain centrifuge - microbiological apparatus and equipment, Explain the C...

Explain the Centrifuge - Microbiological Apparatus and Equipments? Centrifuge is used for separating the substance in liquid or concentrating the microorganisms on the basis of

Can you explain mitotic apparatus, Q. What is mitotic apparatus? Mitoti...

Q. What is mitotic apparatus? Mitotic apparatus is the set of aster fibers, radial structures around each centriole pair, plus the spindle fibers, fibers that extend across the

Study of food texture, Q. Study of food texture? We learnt earlier that...

Q. Study of food texture? We learnt earlier that texture is observed in terms of tactile sensations i.e. finger feel and mouth feel. Finger feel is sensed before ingestion, by

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