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 nutritional properties of the eggs, Explain nutritional properties ...

Explain nutritional properties of the eggs Drying of eggs under normal conditions causes little loss of the nutritional properties of the eggs. Vitamin A, vitamin B, thiamine,

Describe primitive anaerobic eukaryotic cells, Q. How can the hypothesis th...

Q. How can the hypothesis that asserts that chloroplasts as well as mitochondria were primitive prokaryotes that related in mutualism with primitive anaerobic eukaryotic cells be c

Normal pigmentation, The female I-1 and her mate, male I-2, had four childr...

The female I-1 and her mate, male I-2, had four children, one of whom has albinism. What is the probability that they could have had a total of four children with any other outcome

Multiple membrane-spanning proteins, Various integral proteins have multipl...

Various integral proteins have multiple membrane-spanning   -helices. Bacteriorhodopsin, a protein found in a photosynthetic bacterium captures the energy from light and uses it to

State what is genetic engineering, State what is Genetic engineering Ge...

State what is Genetic engineering Genetically engineered plant-incorporated protectants are created by a process that utilizes  several dissimilar modern scientific techniques

Explain antibacterial activity, Antibacterial activity   Rifaximin reach...

Antibacterial activity   Rifaximin reaches high concentrations in the intestinal tract and is active in vitro against a broad range of enteropathogens, including ETEC, EAEC, Shi

What is a biologic failure, What is A biologic Failure A biologic Fail...

What is A biologic Failure A biologic Failure can be defined as the inadequacy of the host to establish or to maintain osseointegration. The inability to establish osseoint

Spiracular control - respiration, Spiracular Control - Respiration ...

Spiracular Control - Respiration Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Liver function test, Liver function test should be done for all diabetic pa...

Liver function test should be done for all diabetic patients. This will help the doctor in the choice of drugs for the treatment of diabetes since liver abnormalities influence the

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