Microbiology with Diseases by Taxonomy Chapter 13 Answers

Microbiology with Diseases by Taxonomy Chapter 13 Answers

Microbiology with Diseases by Taxonomy Answers

Microbiology with Diseases by Taxonomy Chapter 13 Answers 1CM
The following terms are used to prepare concept map:

• +ssRNA
• –ssRNA
• Assembly
• Attachment
• Budding
• dsDNA
• dsRNA
• Endocytosis
• Entry
• Exocytosis
• Fusion
• Host cells
• Lysis
• New virions
• Release
• ssDNA
• Synthesis
• Uncoating
• Viral genome
• Viral nucleic acid
• Viral proteins

The concept map describes the replication of viruses is shown below:

Microbiology with Diseases by Taxonomy Chapter 13 Answers 1CT
Small viruses have single stranded genome and viruses in larger size have double stranded genome. The genome can be either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). The nature of the genome seems to be directly proportionate to the size of the virus. Moreover, small viruses usually do not need more proteins for synthesis of new viruses. Since, very few proteins are needed, the genome of the virus is small and single stranded. Larger viruses need more number of proteins and have a larger genome.
Additionally, family Circoviridae has smallest viral genome, which is single stranded and codes for only 2 proteins. The viruses, which are the larger, are Pandora viruses having double stranded DNA and code for about 2500 proteins.
Therefore, the stranded nature of the genome depends upon the proteins coded by the virus, which is related to the size of the virus.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 1L
The labeled diagram of the lytic replication cycle of the bacteriophage is shown below:

The steps shown above are explained below:

1. Attachment:
   The bacteriophage attaches to the cell membrane of the bacterial cell with the help of the tail fibers.
2. Entry:
   Once the step of attachment is complete, the phage makes a small hole in the cell membrane of the host. The genome of the virus is then pushed inside the cell through this hole. The protein coat is left outside the cell.
3. Synthesis:
   Once the genome of the virus enters the host bacterial cell, it orders the host machinery to start the synthesis of the daughter virions based on the code present in the viral genome.
4. Assembly:
   The different components of the virus are synthesized separately and then fitted together. This step is called assembling of the virus or assembly.
5. Release:
   After the completion of the synthesis of all the daughter virions, the host cell bursts to release the newly synthesized daughter virions into the surroundings.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 1M
The term “uncoating” matches with the phrase “removal of capsomeres from a virion.” Capsomeres are a unit of the protein capsid, which is present in a virus. This protein capsid encloses the genetic material of the virus. The genetic material of a virus can be either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid).
The process of uncoating is the removal of the protein coat from the virus. This is usually seen when the virus infects a host cell. When the virus first begins to infect the host cell, it attaches to the cell with the help of the tail fibers. This step is called attachment.
After the step of attachment, comes the step of uncoating. The genome of the cell slips into the host cell, leaving the protein coat outside the cell. The coat is left attached to the cell membrane, while the genome enters the host cell. Hence, the correct phrase is H. removal of capsomeres from a virion.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 1MC
The following types of organisms are given.
a) Viroid
b) Virus
c) Rickettsia
d) Prion
Out of the following options, all are acellular agents except rickettsia.
a) Viroids are circular fragments of RNA (ribonucleic acid), which have no protein capsid. These viroids cause diseases in plants. Since viroids are not made up of cells, but only made of RNA particles; they are treated as acellular organisms. In addition, they cannot grow, reproduce, or have any metabolic reactions. Hence, option (a) is not the right answer.
b) Viruses are small agents with a nucleic acid of RNA (ribonucleic acid) or DNA (deoxyribonucleic acid) surrounded by a protein coat. Since viruses are not made of cells and only composed of nucleic acid and protein, they are also treated as acellular organisms. In addition, they cannot grow, self-reproduce, or have any metabolic reactions. Hence, option (b) is also not the right answer.
c) Rickettsia is a type of bacteria, which are gram negative, non-motile, and present as a coccus. Since they are bacteria, they have their own metabolizing machinery along with the ability to grow and reproduce unlike acellular agents like viruses and viroids. These organisms have their own DNA and protein and can also synthesize DNA, protein, and other biomolecules. Hence, option (c) is the right answer.
d) Prions are small protein particles, which have the ability to infect. They lack their own DNA, but can convert normal proteins into prions. The diseases caused by prions are usually transmitted by contaminated meat and affect the brain. These diseases are usually incurable. Since these molecules do not have their own DNA and cannot metabolize, they are acellular molecules. Hence, option (d) is not the right answer. Hence, the correct answer is option (c) Rickettsia.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 1SA
The comparison of a bacterium and a virus is given in the following table:

The explanation for the above aspects is given below:
Cell membrane:
A bacterial cell has a cell membrane which encloses all the components of the cell. The cell membrane also protects the cell from environmental factors. A virus does not have a cell membrane. A virus has a capsid to protect the genome of the virus. The other parts of the virus are not enclosed in any sort of membrane.
Functional ribosome:
A bacterial cell has functional ribosomes for the synthesis of protein. A ribosome is an organelle used in the process of protein synthesis. Without the ribosome, a cell cannot synthesize its own proteins. A virus does not have any functional ribosomes. Since the virus uses the machinery of the host for the synthesis of its own proteins, it does not need ribosomes.
Cytoplasm:
A bacterial cell has cytoplasm. Cytoplasm is the fluid-like substance present inside the cell of the bacterium. It also helps in the movement of substances from one part of the cell to another. A virus does not have cytoplasm.
Nucleic acid:
Both bacterial cells and viruses have nucleic acids as their genome. Bacterial cells usually have DNA (deoxyribonucleic acid) as their genome. Viruses can have either DNA or RNA (ribonucleic acid) as their genome. The genome in viruses can be either single stranded or double stranded.
Nuclear membrane:
The nuclear membrane is absent in both bacteria and viruses. Since bacteria are prokaryotes they possess a genome, but do not possess a nucleus or a nuclear membrane. In viruses also, the nuclear membrane is absent.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 2CT
The advantages and disadvantages of the lytic and lysogenic cycles of bacteriophage replication are given below:
Advantages:

1. In the lytic cycle, the release of all new virions at the same time is an advantage to bacteriophage, as surrounding cells can also be infected easily.
2. The lytic cycle is of short duration when compared to the lysogenic cycle.
3. In the lysogenic cycle, the viral genome can be transmitted to the daughters of the bacterial cell.
4. Protection from the environment occurs in the lysogenic cycle when the prophage remains latent.

Disadvantages:

1. Host is killed in lytic cycle, so the bacterial daughter cells cannot be infected by the virus.
2. Replication is longer in the lysogenic cycle.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 2M
The term “prophage” matches with the phrase “inactive virus within bacterial cell.” A virus can undergo either the lytic cycle or the lysogenic cycle after infection of the host cell. There are specific viruses, which undergo lysogeny.
In the lytic cycle, the viral genome forces the host genome to synthesize virions using the host machinery and enzymes. After synthesis of daughter virions, the host cell undergoes lysis or cell death to release the virions into the surrounding matrix. In this cycle, the prophage is not seen.
In the lysogenic cycle, the viral genome integrates with the host genome. It can stay latent and is called a prophage. This viral genome is replicated along with the host genome and can also be transferred to the daughter cells of the host. Sudden changes of environment or any stimulus can reactivate the prophage which will then continue the lytic cycle. Hence, the correct phrase is G. inactive virus within bacterial cell.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 2MC
Out of the given statements, the explanation to show whether they are true or not is given below.
a) “Viruses move towards their host cells.” This statement is false. Viruses usually do not have means of movement outside cells. They can move inside the body of cells with the help of body fluids. But, outside cells, they do not possess pseudopodia or flagella or cilia to help them in moving towards host cells.
b) “Viruses are capable of metabolism.” This statement is false. Since viruses are composed only of nucleic acid and protein, they cannot metabolize. They cannot break down organic molecules or synthesize their own DNA (deoxyribonucleic acid) or protein. They cannot grow or self-reproduce without the help of the host. They use the host enzymes and proteins to synthesize their own proteins.
c) “Viruses lack a cell membrane.” This statement is true. Viruses possess only nucleic acid and protein. They do not possess the basic machinery of the cell or a cell wall or a cell membrane. Viruses contain only a specific kind of nucleic acid along with a protein capsid. Cell membranes are usually present in animal cells, while cell walls are present in plant cells.
d) “Viruses grow in response to their environmental conditions.” This statement is false. Viruses do not grow in response to their environmental conditions. Since viruses do not possess the basic machinery of the cell, they cannot grow like other cells. Unless and until they infect a host cell, they cannot grow or reproduce. They do not have the ability to respond to stimuli from the outer environment like other organisms. Hence, the correct option is (c) viruses lack a cell membrane.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 2SA
The five phases of a generalized lytic replication cycle can be described in the following way:

1. Attachment:
   The bacteriophage needs to come into contact with a bacterial cell for attachment to occur. Contact with a host bacterial cell occurs by random collision. The bacteriophage attaches to the cell membrane of the bacterial cell with the help of the tail fibers. The tail fibers attach to the receptor proteins on the cell membrane of the bacterium.
2. Entry:
   Once the step of attachment is complete, the phage makes a small hole in the cell membrane of the host. This is done by using the enzyme lysozyme. This enzyme weakens the peptidoglycan of the cell membrane. The tail sheath of the phage contracts and forces a hollow tube through the cell wall membrane. The genome of the virus is then pushed inside the cell through this hole. The protein coat is left outside the cell.
3. Synthesis:
   Once the genome of the virus enters the host bacterial cell, it degrades the bacterial genome. The viral genome orders the host machinery to start the synthesis of the daughter virions based on the code present in the viral genome. The process of transcription and translation occur as usual. The enzyme lysozyme is also synthesized which weakens the cell membrane of the bacterium from within. This is necessary for the lysis of the host cell later on in the cycle.
4. Assembly:
   The different components of the virus are synthesized separately and then fitted together. This step is called assembling of the virus or assembly. Sometimes, a piece of the bacterial genome gets incorporated into the daughter virus by mistake. This later leads to a process called transduction.
5. Release:
   By the time assembly ends, the work of lysozyme on the cell membrane is also completed. After the completion of the synthesis of all the daughter virions, the host cell bursts to release the newly synthesized daughter virions into the surroundings.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 3CT
The similarities between computer viruses and biological viruses are given below:

1. Self-spreading nature.
2. Reproductive by causing more number of copies.
3. Spread to other cells/computers.
4. Damage the host.
5. Prevention can be done by antivirus/vaccination.
6. Cannot reproduce on its own that needs a host.

Besides, computer viruses are said to be alive in the computer. Once created, it infects the files and folders on the system. It is created on a computer and can infect the same computer and other computers as well. It can be transferred to other computers through email or any removable discs.
In contrast, biological viruses are said to be dead outside the cell. Outside the host cell, they cannot do anything. Only after infecting a host cell, they can reproduce and synthesize new viruses. Inside a host cell, they are said to be alive.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 3M
The term “retrovirus” matches with the phrase “transcribes DNA (deoxyribonucleic acid) from RNA (ribonucleic acid).”
In most organisms undergoing metabolism, the genome is DNA. This genome contains all the required codes for the synthesis of all proteins, enzymes, and cell components. When a cell wants to synthesize any enzyme, it has to first transcribe the part of DNA, which is specific for that enzyme. In the process of transcription, DNA is converted to RNA. The RNA is then used as a template in the process of translation or protein synthesis.
The flow of genetic information is as shown below:
DNA →  RNA → Protein
In retroviruses, since the genome is RNA, the procedure is bit different. These viruses usually have an enzyme called reverse transcriptase. This enzyme converts the RNA genome into DNA. Since this is a reverse of flow of information, the viruses are called retroviruses. The DNA formed is then incorporated into the genome of the host. Hence, the correct phrase is C. transcribes DNA from RNA.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 3MC
A virus that is specific for a bacterial host is called a phage.
a) A phage is a virus, which infects only bacterial cells. It infects and replicates within bacteria. Usually, phages which infect bacteria undergo either the lytic cycle or the lysogenic cycle. In the lytic cycle, the bacterial host cell ruptures to release the daughter virions. In the lysogenic cycle, the nucleic acid of the virus merges with the nucleic acid of the host. It then undergoes replication along with host DNA (deoxyribonucleic acid). Hence, this option is correct.
b) A prion is a small protein particle, which has the ability to infect. It lacks their own DNA, but can convert normal proteins into prions. The diseases caused by prions are usually transmitted by contaminated meat and affect the brain. These diseases are usually incurable. These prions do not infect bacterial cells. Hence, this option is incorrect.
c) A virion is a complete viral particle. It contains nucleic acid and a capsid. A virus present outside a cell is called a virion. These virions usually obtain their envelope from the membrane of the host. Hence, this option is incorrect.
d) A viroid contains circular fragments of RNA (ribonucleic acid), which have no protein capsid. These viroids cause disease in plants. Since viroids are not made up of cells and only made of RNA particles; they are treated as acellular organisms. In addition, they cannot grow, reproduce or have any metabolic reactions. Hence, this option is incorrect. Hence, the correct option is (a) phage.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 3SA
It is difficult to treat viral infections when compared to bacterial infections.
In the case of bacterial infections, antibiotics given are specific for prokaryotes. Hence, these drugs do not cause any harm to the eukaryotic cells in humans.
In the case of viral infections, viruses multiply inside host cells. Since viruses use the cell machinery, the host cells also need to be destroyed along with the virus. In addition, many viruses have antigenic markers on their capsids. These markers are specific for each virus. These markers are also responsible for the pathogenic nature of the virus.
In many viruses, the structure of these markers is changed repeatedly. A slight change in the sequence coding for these proteins can make a vaccine useless. When a vaccine or a drug is prepared to fight viral infections, a pathogenic protein is taken and drugs are synthesized against it.
This drug can work for some time. But, if the virus has changed the structure of its markers, the drug becomes useless. This is the reason why viral infections are hard to treat.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 4CT
Comparison of lysogeny by prophage and latency by provirus is given below:

1. In the lysogenic cycle, the genome of the virus integrates with the genome of the host cell. In the process of latency seen in animal viruses, the viral genome can either integrate with the host genome or can inactive in the cytosol of the host cell.
2. The viral genome, which inserts into bacterial genomes, is called a prophage, while viral genome inserts into the genome of animal viruses, is called a provirus.
3. In lysogenic viruses, the reactivation of the prophage can occur with change in environment or any other stimuli. This reactivation is known as induction in which the phage DNA (deoxyribonucleic acid) excises from the host genome. The excised prophage follows the lytic cycle, resulting in lysis of the cell. In latency, the reactivation of the provirus occurs when the immune system of the host becomes low. In the example of chicken pox virus, the reactivation causes different disease called herpes zoster.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 4M
The different parts of a bacteriophage are:
Head:
This consists of the protein capsid and the genome enclosed. The protein capsid consists of units called capsomeres. The genome can be either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid).
Tail:
The tail part is the rest of the body of the phage.
Base plate:
This is needed for the attachment of tail fibers to the main body of the virus.
Tail fibers:
These tail fibers are used for attachment of the virus to the cell membrane of the host.
A bacteriophage has been given the name since it infects only bacteria. It is specific for bacteria and does not infect other organisms. Hence, the correct phrase is B. a virus that infects a bacterium.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 4MC
A naked virus has no membranous envelope.
a) A naked virus has no membranous envelope. A virus with an envelope is called an enveloped virus. The envelope on viruses is acquired only after lysis from the host cell. When lysis occurs, each virion gets a part of the host membrane as an envelope. So, the composition of the envelope would be the composition of the bacterial cell membrane. Hence, this option is correct.
b) A naked virus is not a virus, which has injected its DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) into a host cell. When a virus wants to enter a bacterial cell, it attaches to the cell with tail fibers. After attachment, the genome of the virus is injected into the cell, while the empty capsid stays outside. This empty capsid is not called a naked virus. A naked virus is one without a membranous envelope. Hence, this option is incorrect.
c) A naked virus is not devoid of capsomeres. A capsomere is a unit of the capsid. The capsid is made up of many capsomeres. They are made up of protein and enclose the genome of the virus. This capsid remains outside the cell when a virus infects a host cell. A naked virus is one without a membranous envelope. Hence, this option is incorrect.
d) A naked virus is not one, which is unattached to a host cell. A virus, which is unattached to a host, is called only a virus. After a virus infects a host cell, it synthesizes daughter virions inside the host cell. These virions lack a membranous envelope and are called naked viruses. When they are released from the cell, they acquire the host membrane, which becomes the envelope for the virus. Hence, this option is incorrect. Hence, the correct option is (a) has no membranous envelope.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 4SA
The four different ways that viral nucleic acid can enter a host cell are as follows:

1. Entry of viruses into bacterial cells
2. Direct penetration
3. Membrane fusion
4. Endocytosis

The description for the above steps is given below:

1. Entry of viruses into bacterial cells:
   The phage makes a small hole in the cell membrane of the host. This is done by using the enzyme lysozyme. This enzyme weakens the peptidoglycan of the bacterial cell membrane. The tail sheath of the phage contracts and forces a hollow tube through the cell wall membrane. The genome of the virus is then pushed inside the cell through this hole.
2. Direct penetration:
   This process is used by naked viruses. In this method, the viral capsid attaches to receptors on the cell membrane. After attachment, the capsid sinks into the cell membrane. This creates a pore through which the genome enters the cell. The capsid is left outside.
3. Membrane fusion:
   In some viruses, the entire capsid fuses with the cell membrane. This fusion occurs after attachment to cell receptors. The entire capsid is then released into the cell. The glycoproteins of the virus are left as a part of the cell membrane.
4. Endocytosis:
   When the virus attaches to the receptors on the cell membrane of the host, it stimulates the cell to endocytize the entire virus. So, the whole virus enters the host cell. In such methods, the capsid is removed and the viral genome released.

Out of the four different methods given above, the first is regarding the infection of a bacterial host by a virus, while the other three are regarding the infection by animal viruses.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 5CT
In order to stop the viral infection in a crop, an agricultural microbiologist uses the following steps:

1. The onset of a viral infection begins with the attachment of the virus to the host cell. The virus attacks bacterial cell by attaching and then inserting the viral genome into the cell.
2. In the next stage the viral genome either undergoes a lytic cycle or lysogenic cycle. If it undergoes the lytic cycle, the viral genome initially degrades the host genome. Moreover, the host machinery synthesizes the daughter virions. The host cell then bursts to release the daughter virions.
3. In the lysogenic cycle, viral genome incorporates in the genome of the host. It then undergoes divisional cycles along with host genome. Additionally, viral genome is transferred to the host daughter cells. The viral genome is excised from the host genome by a process called induction. This happens due to many reasons like change in environment. After excision, the viral genome follows the lytic cycle as usual.

Thus, beginning step to either the lytic or the lysogenic cycle, attachment of the virus to the host cell. By preventing the attachment, we can prevent viral infections of the crop.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 5M
The term “capsid” matches with the phrase “protein coat of virus.”
The capsid is composed of many capsomeres. Capsomeres are a unit of the protein capsid which is present in a virus. This protein capsid encloses the genetic material of the virus. The genetic material of a virus can be either DNA or RNA.
The process of uncoating is the removal of the protein coat from the virus. This is usually seen when the virus infects a host cell. The coat is left attached to the cell membrane while the genome enters the host cell.
The capsid can be seen in the following figure of a bacteriophage:

Hence, the correct phrase is D. protein coat of virus.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 5MC
Out of the given statements, the explanation to show whether they are true or not is given below.
a) “Viruses may have circular DNA.” This statement is true. The viral families, which have circular genomes, are Baculoviridae, Papovaviridae, and Polydnaviridae. Their genomes may be either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). Circular genomes may be double stranded or single stranded.
b) “dsRNA is found in bacteria more often than in viruses.” This statement is false. In RNA viruses, only the family of Reoviridae has double stranded RNA. The rest of the viral families have single stranded RNA as their genome. In DNA viruses, most of the families contain double stranded DNA. Only, the family Parvoviridae has single stranded DNA as its genome.
c) “Viral DNA may be linear.” This statement is true. The families of Adenoviridae and Herpesviridae have linear DNA as their genome. These genomes may be either DNA or RNA. Linear genomes may be double stranded or single stranded.
d) “Typically, viruses have DNA or RNA, but not both.” This statement is true. Virus families have either DNA or RNA as their genome, but not a combination of both.
Families containing DNA as their genome include Poxviridiae, Herpesviridae, Papillomaviridae, Polyomaviridae, Adenoviridae, Hepadnaviridae, and Parvoviridae.
Families containing RNA as their genome include Picornaviridae, Caliciviridae, Astroviridae, Hepeviridae, Togaviridae, Flaviviridae, Coronoviridae, Retroviridae, Orthomyxoviridae, Paramyxoviridae, Rhabdoviridae, Bunyaviridae, Filoviridae, Arenaviridae, and Reoviridae.
Hence, the only statement, which is false, is option (b) dsRNA is found in bacteria more often than in viruses.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 5SA
The processes of lysis and budding can be compared in the following table:

In both the above processes, the virus multiplies within the host cell and is released. All the steps of the lytic cycle except the last one are also followed in the process of budding. The two processes only differ in the method of release of virions from the host cell.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 6M
The term “envelope” matches with the phrase “a membrane on the outside of a virus.”
An envelope is the outer membrane of a virus. This membrane is acquired when the virus exits the host cell. A virus without a membrane is called a naked virus, while a virus with a membrane is called an enveloped virus.
The envelope of a virus can carry the antigenic markers of the virus. The space between the envelope and the capsid is filled with viral proteins called matrix proteins. The envelope of the virus has the exact components of the host cell membrane. It consists of a phospholipid bilayer with proteins scattered.
The difference between enveloped and non-enveloped viruses is shown below:

Hence, the correct phrase is E. a membrane on the outside of a virus.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 6MC
When a eukaryotic cell is infected with an enveloped virus and sheds viruses slowly, this infection is called a persistent infection.
a) In a lytic infection, soon after infection of the host cell by the virus, the virus takes over the machinery of the host cell. It forces the host cell to synthesize daughter virions. After the synthesis of these virions, the host cell bursts releasing these daughter virions. Hence, this option is incorrect.
b) In a prophage cycle, soon after infection of the host by the virus, the genome of the virus merges with the genome of the host. When this happens, the viral genome is called a prophage. The genome of the virus replicates with the genome of the host and is also transferred to the daughter host cells. Only when there is some sort of environmental change or any sudden stimuli, the prophage excises itself from the genome and continues the lytic cycle. Hence, this option is incorrect.
c) A persistent infection occurs when daughter viruses are released from the host cell by the process of budding. This process is seen only in certain viruses. If all the daughter virions are released at the same time, it is not a persistent infection. But if the budding occurs over a period of time and viruses are being synthesized in the host cell continuously, this is called persistent infection. Hence, this option is correct.
d) A quiescent virus is one, which behaves almost like a lysogenic virus. It remains latent in the host cell after infection. These viruses show non-replicating nature and do not replicate or destroy the host cells. As these viruses are non-replicating, they cannot release daughter virions at all. Hence, this option is incorrect.
Hence, the correct option is (c) called a persistent infection.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 6SA
A virion contains nucleic acid and a capsid. A virus outside a host cell is known as virion. These virions usually obtain their envelope from the membrane of the host. A virion is a complete virus particle present outside the host cell.
A virus particle is one, which usually contains a capsid, genome, and an envelope. It is called a virus only, if it can infect and multiply inside host cells. Viruses can replicate only inside the living cells of the host. A virus can exist in an extracellular and intracellular state. Outside a host cell, a virus cannot replicate or grow on its own.
So, there is not much difference between a virus particle and a virion. Both are complete viral particles with all the components of a virus. A virus is called a virus inside a host cell, while it is called a virion outside a host cell.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 7M
The term “virion” matches with the phrase “complete viral particle.”
A virion is a complete viral particle. It contains nucleic acid and a capsid along with tail fibers. Virions can have an envelope or can be without an envelope. A virus outside a host cell is known as virion. These virions usually obtain their envelope from the membrane of the host.
A complete viral particle has all the components of the virus and is ready to infect other host cells. It has the required genome and the capsid made of protein. The capsid is made up of repeating units called capsomeres.
Incomplete viral particles are those particles, which lack any important component.
Hence, the correct phrase is F. complete viral particle.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 7MC
Another name for a complete virus is virion.
a) A virion is a complete viral particle. It contains nucleic acid and a capsid. Virions can have an envelope or can be without an envelope. A virus outside a host cell is known as virion. These virions usually obtain their envelope from the membrane of the host. Hence, this option is correct.
b) A viroid contains circular fragments of RNA (ribonucleic acid), which have no protein capsid. Since viroids are not made up of cells, but only made of RNA particles, they are not treated as complete viruses. Hence, this option is incorrect.
c) A prion is a small protein particle, which has the ability to infect. It lacks their own DNA (deoxyribonucleic acid), but can convert normal proteins into prions. The diseases caused by prions are usually transmitted by contaminated meat and affect the brain. Since they do not possess a genome, they are not complete viruses. Hence, this option is incorrect.
d) A capsid is the protein coat of the virus. The capsid is made up of many capsomeres. A capsomere is a unit of the capsid. They are made up of protein and enclose the genome of the virus. This capsid remains outside the cell when a virus infects a host cell. Since a capsid does not possess any genome of its own, it is not a complete virus. Hence, this option is incorrect.
Hence, the correct option is (a) virion.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 7SA
A provirus is similar to a prophage in many ways. Both prophages and proviruses have the same method of infecting a host cell. When a virus infects a host cell, its genome is injected into the cell. After this commons step, the genome can follow two ways.

• Lytic cycle
• Lysogenic cycle

In the lytic cycle, the host genome is degraded and the host machinery forced to synthesize new virions. In the end, the host cell bursts and dies.
In the lysogenic cycle, the viral genome integrates with the host genome. This viral genome is then called a prophage. It remains dormant in the genome until external factors activate it. When a virus infects a bacterial cell, it is known as a prophage. A virus is known as a provirus when it integrates with the genome of animal cells. The viral genome remains latent for a period of time.
The only difference between a prophage and a provirus is that a viral genome is called a prophage when it infects bacterial cells. It is called a provirus if it infects animal cells. The term of dormancy is called lysogeny in bacterial cells and latency in animal cells.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 8M
The term “provirus” matches with the phrase “dormant virus in a eukaryotic cell.”
A latent virus is known as a provirus. This virus remains dormant or latent in a eukaryotic cell. It can remain in the cytoplasm of the host cell or can become integrated with the chromosome of the cell. This provirus remains inactive for long periods of time, sometimes even for some years.
When a viral genome gets incorporated into a bacterial cell, it is known as a prophage. But, when a viral genome gets incorporated into a eukaryotic cell, it is known as a provirus. Both have the nature of remaining latent or dormant in the host cells.
In the case of bacterial cells, the process of being dormant is known as lysogeny, while in the case of eukaryotic cells, the process is known as latency. Hence, the correct phrase is A. dormant virus in a eukaryotic cell.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 8MC
Out of the following options, the explanation to show whether the viruses are latent or not is given below.
a) HIV:
The Human Immunodeficiency virus can be latent. When we see the infection by HIV, it is seen that the virus persists in some cells in a latent stage. When the virus lies latent in the host cells, retroviral drugs will not have any effect on HIV. Hence, this option is correct.
b) Chickenpox virus:
The chickenpox virus can be latent. When the chickenpox virus infects a person for the first time, it causes pustules which later on heal. The virus is not totally removed from the body. It lies latent in some nerve ganglion. When it is disturbed or reactivated by any stimulus, it causes the disease herpes zoster along the nerve it is present in. Hence, this option is correct.
c) Herpesviruses:
The herpesviruses can be latent. Chickenpox virus also comes under the category of Herpesviruses. The other latent virus in this category is the Herpes Simplex Virus. This virus also remains latent in neurons. Hence, this option is correct.
d) All of the above:
Since all the given three viruses show latency, we can say that option (d) is the correct option.
Hence, the correct option is (d) all of the above.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 8SA
The process of lysogeny can be described in the following way:

• When a virus infects a cell, it injects its genome into the host cell.
• After the viral genome enters the cell, it integrates with the host genome. This viral genome is then called a prophage.
• It replicates along with the bacterial genome and is passed to the daughter bacterial cells.
• It remains dormant in the genome until external factors activate it. This process is known as induction.
• If it is activated, it then follows the lytic cycle where the host genome is degraded.
• Then, the host machinery is forced to synthesize new virions by using the code of the viral genome.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 9M
The term “benign tumor” matches with the phrase “harmless neoplastic cells.”
A benign tumor is an abnormal growth of cells seen in any part of the body. These tumors usually do not cause any problem since they grow very slowly and do not cause the formation of tumors in other parts of the body. These tumors can only compress the surrounding tissue, but cannot metastasize.
Benign tumors are made up of harmless neoplastic cells, which can be easily removed by surgery. Once removed, usually benign tumors do not return and the patient can live a normal life.
The cause of formation of these tumors might be environmental factors or infection by oncogenic viruses.
Hence, the correct phrase is J. harmless neoplastic cells.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 9MC
Out of the following statements, the explanation to show whether they are specific criteria for the family classification of viruses is given below.
a) The type of nucleic acid present:
The type of nucleic acid, whether it is DNA (deoxyribonucleic acid) or RNA (ribonucleic acid), is a specific criterion in the classification of viruses. Viruses are broadly divided as DNA viruses and RNA viruses based on the genome they possess. Since viruses possess either DNA or RNA but not both, it is a specific criterion for classification. Hence, this option is correct.
b) Envelope structure:
The presence or absence of the envelope acts as a criterion for the classification of viruses. Viruses without envelopes are called naked viruses, while viruses with envelopes are called enveloped viruses. Hence, this option is correct.
c) Capsid type:
The shapes of capsids in viruses are also a criterion in the classification of viruses. The different capsid shapes are helical, polyhedral, and complex. All the different shapes seen fall into these three categories. Hence, this option is correct.
d) Lipid composition:
The lipid composition of the virus is not a criterion for the classification of viruses. Since capsids are mainly made up of protein and the percentage of lipids is less, it cannot be a criterion for the classification of viruses. Hence, this option is incorrect.
Hence, the option (d) lipid composition is not the criterion for the classification of viruses.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 9SA
The envelope of a virus has viral specific glycoproteins and proteins attached to its surface. In the case of non-enveloped viruses, the specific glycoproteins are present on the capsid of the virus.
These specific glycoproteins and proteins act as markers for the recognition of host cells. These glycoproteins recognize the surface receptors on the surface of host cells. By this recognition, some viruses can attack specific host cells.
All viruses are not host-specific, but most of them are. Some viruses like HIV have specific proteins on its surface, which are specific for the receptors on immune cells. That is why HIV attacks the immune system in a person.
Animal viruses are specific for animal cells, while bacteriophages infect bacterial cells.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 10M
The term “cancer” matches with the phrase “invasive neoplastic cells.”
A cancer is an abnormal growth of cells seen in any part of the body. These tumors usually cause problems, since they grow very quickly and cause the formation of tumors in other parts of the body. These tumors can compress the surrounding tissue and can also metastasize.
Cancers are made up of invasive neoplastic cells, which cannot be easily removed by surgery. Once removed, usually cancers return and the patient has to be careful all his life for any signs of cancer in any part of his body.
The cause of formation of these tumors might be environmental factors or infection by oncogenic viruses.
Hence, the correct phrase is I. invasive neoplastic cells.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 10MC
A clear zone of phage infection in a bacterial lawn is a plaque.
a) A prophage:
A prophage is a virus whose genome has integrated with the genome of the host cell. This occurs in the lysogenic cycle. The viral genome replicates along with the bacterial genome and is transmitted to the daughter bacterial cells. This prophage can suddenly reactivate and excise itself from the host genome. It then follows the lytic cycle. Hence, this option is incorrect.
b) A plaque:
When a virus is allowed to infect a lawn of bacterial cells, it causes the formation of clear zones in the lawn. These zones are known as plaques. They represent dead bacterial cells. These plaques indicate that the virus has attacked the bacterial cells in the Petri plate. Hence, this option is correct.
c) Naked:
A virus is called naked when it does not have an envelope. The envelope of a virus is usually acquired from the cell membrane of the host after the lytic cycle. Naked viruses are usually those which are newly synthesized inside the host cell. Those viruses with an envelope are called enveloped viruses. Hence, this option is incorrect.
d) A capsomere:
A capsomere is a unit of the capsid. The capsid is the protein coat which encloses the genome of the virus. It does not play any role in infecting hosts since it is left outside the host cell. A capsomere is present in almost all viruses. Hence, this option is incorrect.
Hence, the correct option is (b) a plaque which is the clear zone of phage infection seen in a bacterial lawn.

Microbiology with Diseases by Taxonomy Chapter 13 Answers 10SA
The comparison of diploid cell culture and continuous cell culture can be described in the following way:

Each method has its own advantages and disadvantages. Hence, it depends on the need of the researcher to use whichever method he thinks best.