QUIZ #2 - PPT (viral replication)

A virus invades a living host cell a thousand times (more/less) its size

more

A virus hijacks the _____________ of the cell to produce copies of itself; and it often destroys the host cell when new __________ are released.

metabolism, virions

Bacteriophages undergo a ___________ or _______________ of infection

lytic or lysogenic cycle

List the steps of viral replication: hhpd

host cell invasion

hijacking metabolism

production of genome copies

destruction of host cells

They are large, complex, naked DNA virions with the characteristic head and tail of bacteriophages

bacteriophages: t2, t4 and t6

Bacteriophages T2, T4, and T6 contain ____________, which function similar to spikes on animal viruses and identify what bacterial species the phage will be able to infect.

tail fibers

The T-even phages are called _______________, meaning they lyse the host cell while carrying out a lytic cycle of infection.

virulent viruses

Viruses invades other cells because the nucleic acid in a phage contains (MANY/ONLY A FEW) of the many genes needed for viral synthesis and replication.

only a few

Viruses (CONTAINS/LACKS) the genes for many other key enzymes, such as for nucleic acid synthesis. Therefore, its dependence on the host cell is substantial.

lacks

State the lytic cycle of bacteriophages in E. Coli: APBMR

Attachment
Penetration
Biosynthesis
Maturation
Release

The phase of Lytic cycle that includes the following steps:

1. Random collision of virulent phages with bacterial cells.
2. Attachment of phage’s tail fiber with complimentary receptor site on cell wall of bacterium.
3. The attachment consists of weak chemical union between phage and receptor site of bacterium.
4. Sometimes bacterium flagellum or pilus act as receptor site

Attachment

The phase of Lytic cycle that includes the following steps:

1. After attachment, the tail of phage release the lysozyme that dissolves the attached portion of cell wall.
2. Tail core drives through the cell wall after the contraction of tail sheath.
3. DNA is ejected through the hollow tail core from the cell membrane into the cell cytoplasm of bacteria.
4. This process takes less than two seconds and capsid remains outside

Penetration

The phase of Lytic cycle that includes the following steps:

1. After entering into cytoplasm phage DNA uses bacterial nucleotide and enzymes to produce multiple copies of genome and capsid.
2. mRNA molecules of phage DNA appears in the cytoplasm and biosynthesizes the phage enzymes along with capsid proteins and amino acids

Biosynthesis

The phase of Lytic cycle that includes the following steps:

1. Once the phage parts are made, they are assembled into complete virus particles.
2. The enzymes encoded by the viral genes guides the assembly in step by step certain fashion.
3. In one area of the host cytoplasm, phage heads and tails are assembled from protein subunits; in another area, the heads are packaged with DNA; and in a third area, the tails are attached to the heads.

Maturation

The phase of Lytic cycle that includes the following steps:

1. Mature phage particles burst out from the ruptured bacterial cell.
2. For some phages, lysozyme, encoded by the bacteriophage genes late in the replicative cycle, degrades the bacterial cell wall.
3. The mature bacteriophages are set free to infect more bacterial cells

Release

Some viruses undergo lysogenic cycle in which viruses do not cause cell lysis and viral DNA interacts with the bacterial chromosome as a __________.

Such bacteriophages are called as ___________.

prophage

temperate phages

Give example of temperate phages:

lambda (λ) phage

Like bacteriophages, animal viruses cause more damage to the animal cell as they cause _________

infection

In animal viruses, there are____________ that are distributed over the capsid and are responsible for the determination of host cell range e.g. HIV & adenovirus.

spikes

Some viruses like HIV and adenoviruses requires a second receptor known as _______________ that help the virus to penetrate into the cytoplasm.

co-receptor

Unlike bacteriophages, in animal viruses, the whole __________ can be taken up into the cytoplasm.

nucleocapsid

For viruses like HIV, the viral __________ fuses with the plasma membrane and releases the nucleocapsid into the cytoplasm.

envelope

Some viruses enter the cell by a process called _________

endocytosis

The process where the capsid disassembles from the genome is called _________

uncoating

After uncoating, the viral genome is transported to the site where __________ or __________ will occur.

transcription, replication

DNA viruses provide the genetic code for enzymes that synthesize __________.

viral parts

__________, a type of DNA virus, replicates entirely in the host cell cytoplasm.

Poxviruses

Most DNA viruses divide tasks between the nucleus and cytoplasm: DNA genomes are synthesized in the __________, and capsid proteins are produced in the __________.

nucleus, cytoplasm

In DNA viruses, capsid proteins are transported to the nucleus and join with __________ molecules for maturation.

nucleic acid

__________ and __________ viruses, both DNA viruses, follow the pattern of dividing tasks between the nucleus and cytoplasm during biosynthesis and maturation.

Adenoviruses, herpesviruses

RNA viruses show a different pattern of __________ and __________ compared to DNA viruses.

biosynthesis, maturation

In +ssRNA viruses, their RNA acts as __________ after uncoating, immediately supplying codes for protein synthesis.

mRNA

For -ssRNA viruses like influenza, their RNA serves as a template to synthesize a complementary __________ strand with the help of RNA-dependent __________.

+ssRNA, polymerase

In -ssRNA viruses, the synthesized +ssRNA serves two purposes: as __________ for protein synthesis and to produce new __________ genomes.

mRNA, -ssRNA

During the maturation of RNA viruses, envelope proteins are synthesized as __________ and are incorporated into either the __________ membrane or the __________ membrane, depending on the virus.

spikes, nuclear, cytoplasmic

In the final stage of replication, enveloped viruses push through the plasma membrane, forcing a portion of the membrane ahead of and around the virion, resulting in an __________

envelope

In enveloped viruses, a membrane-enclosed virus can release the virion by fusing with the plasma membrane in a process known as __________, as seen in the herpes virus. This process need not necessarily kill the cell during release. But with the case of ____________, they leave the cell membrane when it is ruptured and cell death occurs.

budding, naked viruses

Most of the RNA viruses cause productive infection. But many DNA and retroviruses can cause a _____________ which is characterized by the suppression of viral genes i.e. the viral gene remains dormant

latent infection

example of viruses that can generate a productive or latent infection:

herpesviruses (herpes simplex virus-1)

During latency, no viral parts are produced for months or even years until a _______________ reactivates the viral dsDNA.

stress event

In an infected sensory neuron, HSV-1 undergoes latency when its viral dsDNA integrates into the host DNA, forming a __________.

provirus

The provirus is replicated along with the host genome during __________.

cell division

As part of the host genome, the provirus is protected from __________ drugs.

antiretroviral

When the environment is suitable, proviruses are __________ to produce a latent infection.

reactivated