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 the requirement of nutrition during stress, Explain the requirement...

Explain the requirement of Nutrition during Stress? We all experience stress at some time or the other in life. Stress is the condition or stimulus that threatens the body's ho

How do ascaris obtain food, Q. How do ascaris obtain food? An ascaris l...

Q. How do ascaris obtain food? An ascaris live within the human gut and feed from the food ingested by the infected person.

What do you meam by parthenogenesis, Q. What is parthenogenesis? Parthe...

Q. What is parthenogenesis? Parthenogenesis is the formation or reproduction of a new individual from the egg cell but without fecundation by the male gamete. According to the

What are the major structures within the cell nucleus, Within the cell nucl...

Within the cell nucleus the major structures are: the nucleolus, an optically dense region, spherical shaped, where there are concentrated ribosomal RNA (rRNA) associated to protei

Show major arthropod classes, Q. How are the three major arthropod classes ...

Q. How are the three major arthropod classes characterized according to the presence of antennae? Crustaceans have two pairs of antennae insects have one pair arachnids don't h

Pituitary gland, PITUITARY GLAND (HYPOPHYSIS CEREBRI) - It develops ...

PITUITARY GLAND (HYPOPHYSIS CEREBRI) - It develops from ectoderm of the embryo. The pituitary gland is located just below the hypothalamus. The pituitary gland is situate

Describe the terms cellular location and the basic processes, Describe cell...

Describe cellular location and the basic processes of photosynthesis.

How is fecundation done in insects, Q. How is fecundation done in insects (...

Q. How is fecundation done in insects (internal or external)? Is there copulation between insects? Fecundation in insects is internal, with copulation.

Define criteria for assessment of vitamin k status, Define Criteria for Ass...

Define Criteria for Assessment of Vitamin K Status? The parameters of blood clotting time and prothrombin time are used as criteria  to assess vitamin K status as this vitamin

Lungs, LUNG S (PULMONES) - Present in pleural cavity. Covere...

LUNG S (PULMONES) - Present in pleural cavity. Covered by double layered pleura. Outer parietal pleura and inner visceral pleura. Both are continuous, slip on

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