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Lysogenic cycle of viruses

Some viruses, when they infect a host cell, do not destroy it (lytic cycle), but the viral nucleic acid is incorporated into the cellular DNA, where it is replicated and transmitted during successive generations. These viruses are called tempered or attenuated viruses or prophages, and the recipient cell, lysogen cell.

The viral DNA integrated into the bacteria is called a provirus or prophage, and it can remain latent for several generations, until a stimulus (certain inducing agents, usually physical or chemical agents that damage DNA) induces the separation of the prophage, that will start a typical lithic cycle.

Therefore, unlike the lytic cycle, in the lysogenic cycle the virus incorporates its genetic material into the genetic material or genome of the host cell where it can remain latent for an unlimited time (prophage). When it is activated it develops the phases of the lytic cycle.

When the cell contains the prophage, it is immune to other viruses of the same species, and this immunity will be transmitted to subsequent generations, since the prophage is inherited together with the cell's DNA.

Viruses are thought to play an important role in the evolution of species, since when viruses incorporate new genes when infecting a cell, the prophage entails an enrichment of the host cell genotype.

Questions that have come out in University entrance exams (Selectividad, EBAU, EvAU)

Aragon. June 2017, option B, question 4.

Briefly describe the lytic and lysogenic cycles of a virus. (2 points)

Aragon, September 2015, option A, question 1.

Short development topic: viruses. (3 points)

Lytic cycle (description of its phases) and lysogenic cycle of viruses. (2 points)

Aragon. June 2011, option B. 4.

Lysogenic cycle of a phage. (2 points)

Aragon. June 2002, option A. Issue 2.

About viruses:

b) Briefly describe a lysogenic cycle of a virus. (1 point).

Aragon. June 2000, option B. Issue 1 :

Short development topic (2 points):

Viruses: lytic and lysogenic cycle.

Madrid, September 2017, option B, question 5.

Regarding the structure and multiplication of viruses:

b) In relation to the lytic and lysogenic cycles of a bacteriophage, briefly define the following terms: prophage, penetration, assembly, adsorption and synthesis (1.25 points).

Oviedo, June 2019, option B, question 4.

On October 10, 2018, the National Center for Microbiology confirmed that two Spanish adults (who had not traveled to risk countries) contracted the DENGUE disease, caused by a virus that uses as a vector in Spain, among others, the tiger mosquito ( Aedes albopictus ).

a. Define viruses. (Maximum score 0.25).
b. Name and define the structures that make up a virus. (Maximum score 1.0).
c. Name the phases of the life cycle of a virus. Explain the difference between the lytic and lysogenic cycle of a virus. (Maximum score 0.75)

Valencian Community, June 2019, option B, block 4, question 8

Regarding viruses (6 points):

a) Explain the concept of: bacteriophage; viroid and retrovirus;

b) Explain what the lysogenic cycle of viruses consists of. What is the main difference with the lytic cycle?


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