Question

Which bacterial life cycle lacks a dormant stage, proceeding directly to replication, assemble and release. a. conjugation b. the lysogenic cycle e. transformation c. the lytic cycle d. transduction

Answer 1

Answer :- c) The lytic cycle.

Explanation:-

Virus Replication Cycle

While the replication cycle of viruses can vary from virus to virus, there is a general pattern that can be described, consisting of five steps:

1.Attachment – the virion attaches to the correct host cell.

2.Penetration or Viral Entry – the virus or viral nucleic acid gains entrance into the cell.

3.Synthesis – the viral proteins and nucleic acid copies are manufactured by the cells’ machinery.

4.Assembly – viruses are produced from the viral components.

5.Release – newly formed virions are released from the cell.

Bacteriophage

Virusesthat infect bacteria are known as bacteriophage or phage. A virulent phage is one that always lyses the host cell at the end of replication, after following the five steps of replication described above. This is called the lytic cycle of replication.

Thereare also temperate phage, viruses that have two options regarding their replication. Option 1 is to mimic a virulent phage, following the five steps of replication and lysing the host cell at the end, referred to as the lytic cycle. But temperate phage differ from virulent phage in that they have another choice: Option 2, where they remain within the host cell without destroying it. This process is known as lysogeny or the lysogenic cycle of replication.

Aphage employing lysogeny still undergoes the first two steps of a typical replication cycle, attachment and penetration. Once the viral DNA has been inserted into the cell it integrates with the host DNA, forming a prophage. The infected bacterium is referred to as a lysogen or lysogenic bacterium. In this state, the virus enjoys a stable relationship with its host, where it does not interfere with host cell metabolism or reproduction. The host cell enjoys immunity from reinfection from the same virus.

Exposureof the host cell to stressful conditions (i.e. UV irradiation) causes induction, where the viral DNA excises from the host cell DNA. This event triggers the remaining steps of the lytic cycle, synthesis, maturation, and release, leading to lysis of the host cell and release of newly formed virions.

Conclusion:- So lytic cycle has no dormancy stage but lysogenic cycle have dormancy stage.

Bacterial recombination is a type of genetic recombination in bacteria characterized by DNA transfer from one organism called donor to another organism as recipient. This process occurs in three main ways:

• Transformation,
• Transduction, and
• Conjugation.
• So these three steps are genetic recombination process.
  Lytic cycle Host bacterial cell Bacteriophage Phage DNA Host DNA The phage infects a cell The phage DNA circularizes, remaining separate from the host DNA. Phage DNA replicates and phage proteins are made. New phage particles are assembled The cell lyses, releasing phage. Lysogenic cycle The phage infects a cell The phage DNA becomes incorporated into the host genome The cell divides, and prophage DNA is passed on to daughter cells Under stressful conditions, the phage DNA is excised from the bacterial chromosome and enters the lytic cycle