Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 1341: Viral DNA is integrated into Bacterial DNA in:

A. Lysogenic cycle (Correct Answer)
B. Bacterial transduction
C. Bacterial transformation
D. Bacterial conjugation

Explanation: ***Lysogenic cycle*** - In the **lysogenic cycle**, the **bacteriophage DNA integrates** into the host bacterial chromosome, becoming a **prophage**. - This integration allows the viral genome to be **replicated along with the host DNA** without immediately lysing the cell. *Bacterial transduction* - **Transduction** involves the transfer of **bacterial DNA** from one bacterium to another via a bacteriophage, not the integration of viral DNA into the host genome. - While phages are involved, the primary event is the accidental packaging and transfer of bacterial genes, not viral integration into the host for replication. *Bacterial transformation* - **Transformation** is the process where bacteria take up **naked DNA from their environment** and incorporate it into their own genome. - This DNA is typically from another bacterium or is artificially introduced, not viral DNA undergoing a natural integration process within the cell. *Bacterial conjugation* - **Conjugation** is the transfer of genetic material (usually a **plasmid**) between bacteria through direct cell-to-cell contact, mediated by a **pilus**. - This process involves the transfer of bacterial or plasmid DNA, not the integration of a viral genome into the host chromosome.

Question 1342: Which of the following statements about paramyxoviruses is false?

A. Belong to the family Paramyxoviridae
B. Are DNA viruses (Correct Answer)
C. Are RNA viruses
D. Have linear nucleic acid

Explanation: ***Are DNA viruses*** - Paramyxoviruses are characterized by their **single-stranded, negative-sense RNA genome**, not DNA. - Their replication and transcription processes occur in the cytoplasm, which is typical for RNA viruses. *Belong to the family Paramyxoviridae* - This statement is correct; paramyxoviruses are indeed classified under the **family Paramyxoviridae**. - This family includes important human pathogens like measles, mumps, and respiratory syncytial virus (RSV). *Have linear nucleic acid* - This statement is correct as paramyxoviruses possess a **linear, non-segmented RNA genome**. - The linear nature differentiates them from viruses with segmented genomes, such as influenza viruses. *Are RNA viruses* - This statement is correct; paramyxoviruses are characterized by their **RNA genome**. - Specifically, they are **negative-sense, single-stranded RNA viruses**.

Question 1343: Which of the following can infect the ovary?

A. Mumps virus (Correct Answer)
B. Epstein-Barr Virus (EBV)
C. Cytomegalovirus (CMV)
D. Measles virus

Explanation: ***Mumps virus*** - The mumps virus can cause **oophoritis** (inflammation of the ovary) in post-pubertal females, though it is less common than orchitis in males. - Oophoritis typically presents with **lower abdominal pain** and tenderness, often accompanied by fever and other mumps symptoms like parotitis. *Epstein-Barr Virus (EBV)* - While EBV causes **infectious mononucleosis** and is associated with various lymphomas and nasopharyngeal carcinoma, it is not a primary cause of direct ovarian infection. - EBV primarily targets **B lymphocytes** and epithelial cells, and ovarian involvement is not a typical manifestation. *Cytomegalovirus (CMV)* - CMV can cause a wide range of infections, particularly in **immunocompromised individuals** and neonates, leading to congenital abnormalities. - Although CMV can infect many organs, direct infection of the ovary leading to oophoritis is **extremely rare** and not a recognized clinical entity. *Measles virus* - The measles virus primarily causes a systemic infection characterized by a **maculopapular rash**, fever, cough, coryza, and conjunctivitis. - While it can lead to complications such as pneumonia or encephalitis, **ovarian involvement or oophoritis** is not a known or common complication of measles.

Question 1344: Which HIV virus is associated with a higher transmission rate and virulence?

A. Both have similar risks
B. It depends on individual factors
C. HIV-2
D. HIV-1 (Correct Answer)

Explanation: ***HIV-1*** - **HIV-1** is responsible for the vast majority of HIV infections worldwide and is known for its **higher virulence** and more rapid progression to AIDS. - It also has a **higher transmission rate** compared to HIV-2, contributing to its global prevalence. *HIV-2* - **HIV-2** is less virulent and has a **slower progression** to AIDS compared to HIV-1. - Its transmission rate is **lower** than HIV-1, and it is primarily concentrated in West Africa. *Both have similar risks* - This statement is incorrect because **HIV-1 and HIV-2 differ significantly** in their transmission rates, virulence, and disease progression. - **HIV-1** poses a much greater global health burden due to its higher infectivity and pathology. *It depends on individual factors* - While individual factors can influence disease progression, the intrinsic characteristics of **HIV-1** and **HIV-2** (such as transmissibility and virulence) are distinct and not solely dependent on the host. - The inherent biological differences between the two viruses are the primary determinants of their differential impact.

Question 1345: Which of the following is not a poxvirus?

A. Molluscum contagiosum
B. Orf virus
C. Vaccinia virus
D. Coxsackie virus (Correct Answer)

Explanation: ***Coxsackie virus*** - The **Coxsackie virus** belongs to the family **Picornaviridae**, not Poxviridae. - It is known for causing diseases such as **hand, foot, and mouth disease**, herpangina, and myocarditis. *Vaccinia virus* - **Vaccinia virus** is a well-known member of the **Poxviridae** family, historically used in the smallpox vaccine. - It is a **large, complex DNA virus** that replicates in the cytoplasm of infected cells. *Molluscum contagiosum* - **Molluscum contagiosum virus (MCV)** is a **poxvirus** that causes a mild skin infection characterized by raised, pearly, umbilicated lesions. - It primarily infects **humans**, causing localized lesions that are spread through direct contact. *Orf virus* - **Orf virus**, also known as contagious pustular dermatitis virus, is a **poxvirus** that primarily affects sheep and goats. - It can be transmitted to humans, causing single papular or nodular lesions, usually on the fingers, hands, or forearms.

Question 1346: Which strain of the Influenza A virus, not of human origin, has the highest pandemic potential?

A. H1N1
B. H9N2
C. H2N2
D. H5N1 (Correct Answer)

Explanation: ***H5N1*** - The **H5N1 avian influenza virus** is widely considered to have high pandemic potential due to its ability to cause severe disease and high mortality in humans, despite limited human-to-human transmission. - It circulates extensively in **poultry populations**, providing ample opportunity for zoonotic spillover. *H1N1* - While H1N1 caused the **2009 swine flu pandemic**, the question specifies a strain "not of human origin" with high pandemic potential, and H1N1 is an avian-origin reassortant that adapted to humans. - Current circulating seasonal H1N1 strains already have some human immunity, reducing their pandemic potential. *H2N2* - The **H2N2 strain** caused the 1957 "Asian Flu" pandemic, and current human populations have some immunity due to previous exposure to related strains in circulation. - It is no longer circulating in humans and its pandemic potential is lower compared to novel highly pathogenic avian strains like H5N1. *H9N2* - **H9N2** is a low-pathogenic avian influenza virus that has caused sporadic human infections, primarily in agricultural workers. - While it has zoonotic potential, its infections in humans are typically mild and its capacity for sustained human-to-human transmission remains very limited, indicating lower pandemic potential than H5N1.

Question 1347: Which of the following viruses is a member of the Herpesviridae family?

A. Variola
B. Adenovirus
C. HPV
D. Herpes Simplex Virus (Correct Answer)

Explanation: ***Herpes Simplex Virus*** - **Herpes Simplex Virus (HSV)** is the type species of the *Herpesviridae* family, which includes other common human pathogens such as **cytomegalovirus** and **Epstein-Barr virus**. - Members of this family are characterized by a **double-stranded DNA genome**, an icosahedral capsid, and an envelope, and they typically cause **latent infections**. *Variola* - **Variola virus** is a member of the *Poxviridae* family, known for causing **smallpox**, a historically devastating disease. - Unlike herpesviruses, poxviruses are **large and complex DNA viruses** that replicate entirely in the cytoplasm of infected cells. *Adenovirus* - **Adenovirus** belongs to the *Adenoviridae* family and is a **non-enveloped DNA virus** known for causing a variety of conditions, including respiratory infections and conjunctivitis. - Its structure and replication cycle differ significantly from the enveloped *Herpesviridae*. *HPV* - **HPV (Human Papillomavirus)** is a member of the *Papillomaviridae* family, which are small **non-enveloped DNA viruses** associated with warts and certain cancers. - It is distinct from herpesviruses in its genomic organization, capsid structure, and disease manifestations.

Question 1348: HIV envelope is formed by:

A. Host cell
B. Virus
C. Both (Correct Answer)
D. None of the options

Explanation: ***Both (Correct Answer)*** - The HIV envelope is a **composite structure** derived from both host and viral components - The **lipid bilayer** is acquired from the **host cell membrane** during viral budding - **Viral glycoproteins (gp120 and gp41)** encoded by the viral genome are inserted into this host-derived membrane - This makes the envelope a true hybrid structure essential for viral infectivity *Host cell (Incomplete)* - While the **lipid bilayer** of the envelope comes from the host cell membrane during budding, this alone does not form a functional envelope - The host cell provides the membrane scaffold but lacks the viral glycoproteins necessary for receptor binding and cell entry - Without viral proteins, the envelope cannot mediate infection *Virus (Incomplete)* - The virus encodes essential **envelope glycoproteins** (gp120 for receptor binding, gp41 for membrane fusion) - However, the virus does **not synthesize the lipid bilayer** itself - The viral genome lacks genes for lipid synthesis; the membrane must be acquired from the host *None of the options* - This is incorrect as the HIV envelope clearly requires contributions from **both** the host cell (lipid membrane) and the virus (glycoproteins)

Question 1349: Which is not a DNA virus?

A. Rhabdovirus (Correct Answer)
B. Poxvirus
C. Papovavirus
D. Parvovirus

Explanation: ***Rhabdovirus*** - Rhabdoviruses, such as the rabies virus, are characterized by their **single-stranded RNA genome** and distinctive bullet-shaped morphology. - They replicate in the cytoplasm of infected cells, using their **RNA-dependent RNA polymerase** to transcribe their genome. *Papovavirus* - Papovaviruses (now split into Papillomaviridae and Polyomaviridae) are **DNA viruses** known for causing warts and some cancers. - They possess a small, **double-stranded, circular DNA genome**. *Poxvirus* - Poxviruses are large, complex **DNA viruses** that replicate entirely within the cytoplasm of the host cell. - They have a **double-stranded DNA genome** and are notable for causing diseases like smallpox and molluscum contagiosum. *Parvovirus* - Parvoviruses are among the smallest viruses, characterized by their **single-stranded DNA genome**. - They require actively dividing host cells to replicate their **linear DNA**.

Question 1350: Most common type of HPV associated with cervical cancer?

A. 6, 11
B. 5, 8
C. 16, 18 (Correct Answer)
D. 6, 8

Explanation: ***16, 18*** - **HPV types 16 and 18** are considered **high-risk HPV types** and are responsible for approximately **70% of all cervical cancer cases** globally. - These types produce **oncoproteins E6 and E7** that interfere with tumor suppressor genes (p53 and Rb), leading to uncontrolled cell growth and malignancy. *6, 11* - **HPV types 6 and 11** are considered **low-risk HPV types** and are primarily associated with **genital warts (condyloma acuminata)**. - While they can cause benign lesions, they are **rarely associated with cervical cancer**. *5, 8* - **HPV types 5 and 8** are **cutaneous HPV types** primarily associated with **epidermodysplasia verruciformis**, a rare genetic condition predisposing to skin cancers. - These types affect the **skin** and are **not associated with cervical cancer**, making them incorrect for this question. *6, 8* - This combination includes **HPV 6**, which is a **low-risk type** primarily associated with genital warts. - **HPV 8** is a cutaneous type associated with skin lesions, not cervical cancer. - This pairing does not represent the most common types responsible for cervical cancer.

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Virus Structure and Classification

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Pathogenesis of Viral Infections

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DNA Viruses: Herpesviruses

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DNA Viruses: Poxviruses and Adenoviruses

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Hepatitis Viruses

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RNA Viruses: Orthomyxoviruses

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RNA Viruses: Paramyxoviruses

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Enteroviruses and Rhinoviruses

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Arboviruses

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HIV and Retroviruses

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Oncogenic Viruses

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Virology — MCQs

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