Experimental studies reveal that double-stranded DNA can exist in three different helical forms known as A, B, and Z DNA. Why do
2 answers:
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Complete question:
The diagram to the right represents the lytic cycle. What is occurring at step C?
- The pieces made in replication are assembled to complete the new virus particles.
- The virus attaches to the host cell.
- The host's DNA is disassembled and the virus takes over the cell's metabolic activity.
- The new viral nucleic acid and viral proteins are replicated.
- Lysis occurs, killing the cell.
Answer:
4. The new viral nucleic acid and viral proteins are replicated
Explanation:
During the lytic cycle, a host cell is infected by a virus. The infected cell dies by lysis of the cell membrane while the new copies of the virus are being released. The lytic cycle is the principal viral reproductive method and involves the destruction of the infected cells.
The lytic cycle is composed of five steps:
<u>Attachment phase</u>:
Viruses recognize specific receptors in the membrane of the host cells, where they get attached. These receptors are glycoproteins or lipoproteins that join viral elements and hold them on the host surface.
<u>Penetration phase</u>:
Viruses use different mechanisms to penetrate the host cells.
- By injection, by perforating the host cell wall and membrane and injecting the genetic material through a hole. The rest of the virus remains outside the cell.
- By endocytosis. The virus introduces by complete into the host cell by endocytosis of the membrane. Once inside, the virus breaks the vesicle membrane and gets in contact with the cytoplasm.
- By fusing with the membrane
- By going through the pores
Biosynthesis phase (replication and synthesis of the viral components)
There are no viral copies yet, but DNA, RNA, and proteins are being produced.
The host cell metabolism is used to synthesize viral elements. Viral nucleic acid uses the host cell nucleotides and RNA polymerase to synthesize mRNA and produce proteins and enzymes to destroy the infected cell DNA.
The viral nucleic acid duplicates and new proteins are produced.
<u>Maturation phase</u>
In this stage occurs the Assembling of the newly synthesized viral components. Many viral copies are formed.
<u>Lysis phase</u>
This is the moment in which the new viral copies get released. They break the host cell membrane by lysis through the action of the endolysin enzyme. Lysis produces the host cell death.
In the exposed diagram you can recognize
A) Attachment phase and penetration by injection phase
B) Biosynthesis phase → destruction of the host DNI. The host cell metabolism is used to synthesize viral elements
C) Biosynthesis phase → Viral components (nucleic acid + proteins) are already replicated.
D) Maturation and Lysis phase
E) Infection of a new host cell by attaching to its membrane
