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

Chilling and flower induction, Chilling and Flower Induction Some plan...

Chilling and Flower Induction Some plants flower only after passing a winter season. For example, winter wheat is sown in the autumn for harvest in the following summer. It ne

What is juvenile mitral stenosis, Q. What is Juvenile Mitral Stenosis ? ...

Q. What is Juvenile Mitral Stenosis ? Peculiar to developing countries is the problem of juvenile mitral stenosis. Patients with rheumatic fever develop tight mitral stenosis i

Most abundant form under which nitrogen is found in nature, Q. What is the ...

Q. What is the most abundant form under which nitrogen is found in nature? The major abundant nitrogen-containing molecule found in nature is molecular nitrogen (N2). The air i

Explain about the cyclamate - artificial sweeteners, Explain about the cycl...

Explain about the cyclamate - artificial sweeteners? Another sweetener is cyclamate (sodium cyclohexylsulphamate). Have a look at its structure as shown in the figure. It is on

Hydration control by active pump mechanisms in corneal, How is hydration co...

How is hydration control by active pump mechanisms responsible in the corneal hydration? Hydration Control by Active Pump Mechanisms: a) Na/K ATPase pump, which is more acti

Chloroplasts , Chloroplasts Like mitochondria, chloroplasts are also di...

Chloroplasts Like mitochondria, chloroplasts are also distinctive organelles of eucaryotic cell. But they are found only in plant cells. Chloroplasts contain membranes forming

Endocytosis and exocytosis, Endocytosis and Exocytosis Endocytosis is the...

Endocytosis and Exocytosis Endocytosis is the process by which substances are brought into the cell from outside by formation of membrane bound vesicles. These extra cellular sub

What functions performed by vitamin and mineral for athletes, What function...

What functions performed by Vitamin and Mineral for athletes? Vitamins and minerals perform the same essential functions for athletes and non-athletes alike. However, owing t

Development and differentiation of a flowering plant, Development and Diffe...

Development and Differentiation of a flowering plant The developmental phases of a flowering plant involve seed germination, vegetative growth, flowering, fruiting and senesce

The heart, Ask question #Minimum 100 words adccepted#

Ask question #Minimum 100 words adccepted#

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