Question

This is about the measles virus. (a paramyxovirus)

FILL IN THE BLANK: 1. During attachment, viral [name viral ligand] binds receptor molecules on the cell] of the host cell [name specific structure of host 2. During [name stage of replication] and uncoating, the virion enters the cell by membrane genome into the cytoplasm of the cell [name process], releasing the 3. During biosynthesis, the [positive or negative] strand RNA genome is replicated using the viral [name specific enzyme] that [was or was not] packaged inside the infecting virion. This activity will also produce that will be translated to produce viral structural proteins. [name the specific macromolecule] 4. During assembly, viral surface proteins are exported to the host cell structure] where they will aggregate with other viral proteins and genome copies. 5. During release, infectious virions leave the host cell by the process of [name [name process], acquiring its [name viral structural component] from the host cell as it leaves. QUESTIONS TO ANSWER: 6. Would you expect the measles viral genome to acquire more mutations during replication than the genome of a DNA virus would? Explain. 7. The measles vaccine is impressively effective, with 99% of people protected against measles after 2 doses. The active ingredient is "live" measles virus that has been attenuated, meaning it replicates poorly inside its usual host cells. However, because the virus is able to replicate a little, it stimulates a robust immune response and lasting immunity. To attenuate the virus, it is replicated inside a chick embryo cell line grown in tissue culture. Eventually, after rounds of replication and adaptation to chick cells, the virus ceases to replicate well in human cells Name one structural component of the virus that, if altered during serial passage on chick cells, could give rise to cells that no longer replicate well in a human host. Explain how mutation of this structural component could lead to a switch in host cell preference FILL IN THE BLANK: 1. During attachment, viral [name viral ligand] binds receptor molecules on the cell] of the host cell [name specific structure of host 2. During [name stage of replication] and uncoating, the virion enters the cell by membrane genome into the cytoplasm of the cell [name process], releasing the 3. During biosynthesis, the [positive or negative] strand RNA genome is replicated using the viral [name specific enzyme] that [was or was not] packaged inside the infecting virion. This activity will also produce that will be translated to produce viral structural proteins. [name the specific macromolecule] 4. During assembly, viral surface proteins are exported to the host cell structure] where they will aggregate with other viral proteins and genome copies. 5. During release, infectious virions leave the host cell by the process of [name [name process], acquiring its [name viral structural component] from the host cell as it leaves. QUESTIONS TO ANSWER: 6. Would you expect the measles viral genome to acquire more mutations during replication than the genome of a DNA virus would? Explain. 7. The measles vaccine is impressively effective, with 99% of people protected against measles after 2 doses. The active ingredient is "live" measles virus that has been attenuated, meaning it replicates poorly inside its usual host cells. However, because the virus is able to replicate a little, it stimulates a robust immune response and lasting immunity. To attenuate the virus, it is replicated inside a chick embryo cell line grown in tissue culture. Eventually, after rounds of replication and adaptation to chick cells, the virus ceases to replicate well in human cells Name one structural component of the virus that, if altered during serial passage on chick cells, could give rise to cells that no longer replicate well in a human host. Explain how mutation of this structural component could lead to a switch in host cell preference

Answer 1

1. Adsorption is the first stage of the viral replication that refers to the attachment of viral proteins to the cell surface receptors of host cell. Here, the process requires expression of specific protein ligands in viruses which bind to the host cell receptors that are embedded in the plasma membrane of host cell. G protein serve as viral protein ligands and interact with cell surface receptor present on plasma membrane or cell membrane of host cell followed by uncoating.

During attachment, viral G attachment protein binds to receptor molecules on the plasma membrane of host cell.