Virology Practice Questions

Q: Which of the following contains an RNA-dependent DNA polymerase as a structural component of the virion?

RNA tumor viruses. **Explanation:** The correct answer is **RNA tumor viruses** (Retroviruses). **1. Why RNA tumor viruses are correct:** RNA tumor viruses, such as Human T-cell Lymphotropic Virus (HTLV) and HIV, belong to the **Retroviridae** family. These viruses are unique because they possess the enzyme **Reverse Transcriptase (RNA-dependent DNA polymerase)** as an integral structural component within the viral capsid. This enzyme allows the virus to transcribe its single-stranded RNA genome into double-stranded DNA, which then integrates into the host cell's genome (provirus). This step is essential for replication and oncogenic transformation. **2. Why the other options are incorrect:** * **Adenoviruses (Option A):** These are non-enveloped **dsDNA** viruses. They use host cell DNA-dependent DNA polymerase for replication and do not require reverse transcriptase. * **Orthomyxoviruses (Option B):** (e.g., Influenza virus) These are negative-sense ssRNA viruses. They carry an **RNA-dependent RNA polymerase** (RdRp) to synthesize mRNA, but they do not produce DNA intermediates. * **Rhabdoviruses (Option C):** (e.g., Rabies virus) Like Orthomyxoviruses, these are negative-sense ssRNA viruses that carry their own **RNA-dependent RNA polymerase** (RdRp) within the virion, not a DNA polymerase. **High-Yield Clinical Pearls for NEET-PG:** * **Reverse Transcriptase** has three activities: RNA-dependent DNA polymerase, RNase H (degrades RNA from RNA-DNA hybrid), and DNA-dependent DNA polymerase. * **Hepatitis B Virus (Hepadnaviridae)** also uses reverse transcriptase during its replication cycle, but unlike Retroviruses, it is a **DNA virus** that packages the enzyme to convert an RNA intermediate back into DNA. * **RNA-dependent RNA polymerase** is a structural component of all **negative-sense RNA viruses** (e.g., Ortho-, Paramyxo-, Rhabdo-, Filo-, and Bunyaviruses).

Q: Evaluation of a specimen from a patient with hepatocellular carcinoma demonstrates the presence of a single-stranded RNA virus. Which of the following is the most probable etiological agent?

Hepatitis C virus. ### Explanation The correct answer is **Hepatitis C virus (HCV)**. **1. Why Hepatitis C is correct:** Hepatitis C is a **single-stranded RNA (ssRNA)** virus belonging to the *Flaviviridae* family. It is a major risk factor for the development of Hepatocellular Carcinoma (HCC). Unlike DNA viruses, HCV does not integrate into the host genome; instead, it promotes oncogenesis through chronic inflammation, oxidative stress, and the action of non-structural proteins (like NS5A) that interfere with cell cycle regulation and apoptosis. Active infection is confirmed by the presence of serum hepatitis C RNA [1]. **2. Why other options are incorrect:** * **Hepatitis B virus (HBV):** While HBV is a leading cause of HCC worldwide, it is a **partially double-stranded DNA virus** (*Hepadnaviridae*). It can cause HCC even without cirrhosis due to its ability to integrate into the host DNA. * **Hepatitis A (HAV) and Hepatitis E (HEV):** Both are RNA viruses transmitted via the fecal-oral route [3]. However, they cause **acute hepatitis** only and do not lead to chronic infection, cirrhosis, or an increased risk of HCC. (Note: HEV can be chronic in immunocompromised patients, but it is not typically linked to HCC). **3. High-Yield Clinical Pearls for NEET-PG:** * **Genome Type:** Remember the mnemonic "All Hepatitis viruses are RNA except **B** (DNA)." * **HCC Risk:** In the presence of cirrhosis, HCV has a higher annual risk of progressing to HCC compared to HBV. * **Screening:** Patients with chronic HCV and cirrhosis should undergo HCC surveillance every 6 months using **Ultrasonography +/- Alpha-fetoprotein (AFP)** [2]. * **Treatment:** Direct-acting antivirals (DAAs) can achieve a Sustained Virologic Response (SVR), significantly reducing but not entirely eliminating the risk of HCC.

Q: Which of the following does not indicate Hepatitis B replication?

HBcAg. **Explanation:** The correct answer is **HBcAg (Hepatitis B core Antigen)**. In clinical practice, **HBcAg is not detectable in the serum** because it is sequestered within the viral envelope (HBsAg). It remains localized within the hepatocyte nuclei. Therefore, its presence in a standard blood report cannot be used to monitor active viral replication. Instead, we measure **Anti-HBc antibodies** to determine exposure. **Why the other options are markers of replication:** * **HBeAg (Hepatitis B envelope Antigen):** This is a soluble protein secreted by the virus during active replication. Its presence in serum indicates high infectivity and active viral multiplication. * **HBV DNA:** This is the most sensitive and specific quantitative marker for viral load. It directly measures the genetic material of the virus in the blood. * **Viral copies:** This is simply the numerical quantification of HBV DNA. High copy numbers correlate directly with active replication and the risk of liver damage. **NEET-PG High-Yield Pearls:** 1. **Window Period:** The time between the disappearance of HBsAg and the appearance of Anti-HBs. During this phase, **Anti-HBc IgM** is the only diagnostic marker present. 2. **Pre-core Mutant:** A condition where the patient is HBeAg negative but has high HBV DNA levels. This occurs due to a mutation in the pre-core region that prevents HBeAg secretion despite active replication. 3. **HBsAg:** The first marker to appear in blood after infection; its persistence beyond 6 months defines chronic hepatitis B. 4. **Anti-HBs:** Indicates immunity (either through recovery or vaccination).

Q: Which of the following viruses is brick-shaped?

Small pox. **Explanation:** The correct answer is **Smallpox (Variola virus)**. **1. Why Smallpox is correct:** Smallpox belongs to the **Poxviridae** family. Poxviruses are the largest and most complex of all animal viruses. Under electron microscopy, they exhibit a characteristic **brick-shaped** (rectangular) morphology with a complex internal structure consisting of a biconcave core and two lateral bodies. This is a classic high-yield morphological feature often tested in NEET-PG. **2. Why the other options are incorrect:** * **Chickenpox (Varicella-Zoster Virus), CMV (Cytomegalovirus), and EBV (Epstein-Barr Virus):** All three belong to the **Herpesviridae** family. Herpesviruses are characterized by an **icosahedral** capsid symmetry and are **spherical** in overall shape due to their lipid envelope. They are significantly smaller than poxviruses. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Size:** Poxviruses are the only viruses large enough to be seen under a light microscope (using special stains like Paschen’s stain). * **Replication:** Unlike most DNA viruses that replicate in the nucleus, Poxviruses replicate entirely in the **cytoplasm** because they carry their own DNA-dependent RNA polymerase. * **Inclusion Bodies:** Smallpox produces intracytoplasmic inclusion bodies known as **Guarnieri bodies**. * **Eradication:** Smallpox is the only human infectious disease to be globally eradicated (declared by the WHO in 1980). * **Molluscum Contagiosum:** Another member of the Poxviridae family, it also shares the brick-shaped morphology and produces Henderson-Patterson bodies.

Q: Which of the following statement is TRUE about polio?

Increased muscular activity leads to increased paralysis. **Explanation:** The correct answer is **C: Increased muscular activity leads to increased paralysis.** This is a high-yield concept in Polio pathogenesis known as **"Provocation Polio."** During the pre-paralytic stage of the infection, excessive physical activity or muscular trauma (like IM injections) increases the risk and severity of paralysis in the specific muscle groups involved. This occurs because increased metabolic activity in the motor neurons facilitates the entry and replication of the poliovirus within the anterior horn cells of the spinal cord. **Analysis of Incorrect Options:** * **A. Paralytic polio is most common:** Incorrect. In reality, **Inapparent/Asymptomatic infection** is the most common outcome (>90-95%). Paralytic polio occurs in less than 1% of cases. * **B. Spastic paralysis:** Incorrect. Poliovirus specifically destroys the **Lower Motor Neurons (LMN)** in the anterior horn of the spinal cord. This results in **Asymmetrical Flaccid Paralysis** with loss of deep tendon reflexes, not spasticity. * **D. Polio vaccine is given orally:** While the Oral Polio Vaccine (OPV/Sabin) is given orally, this option is considered "less true" in a competitive context compared to the physiological fact in Option C. Furthermore, the global shift (including India’s Universal Immunization Programme) now emphasizes the **Inactivated Polio Vaccine (IPV)**, which is given via IM or intradermal routes. **High-Yield Clinical Pearls for NEET-PG:** * **Specimen of choice:** Stool (virus is excreted for weeks). * **Most common site of paralysis:** Spinal (legs > arms). * **Post-Polio Syndrome:** Occurs 30–40 years after recovery due to the gradual failure of over-extended motor neurons. * **Last case in India:** 13th January 2011 (Howrah, West Bengal). India was declared Polio-free in 2014.

Q: Which virus has a segmented genome?

Rotavirus. **Explanation:** The concept of a **segmented genome** is a high-yield topic in virology. Most viruses have a single continuous piece of nucleic acid, but some RNA viruses have genomes divided into separate pieces (segments). This allows for **genetic reassortment**, leading to significant antigenic shifts. **1. Why Rotavirus is Correct:** Rotavirus belongs to the **Reoviridae** family. It is characterized by a **double-stranded RNA (dsRNA)** genome consisting of **11 segments**. This segmentation is crucial for its genetic diversity. Clinically, Rotavirus is the most common cause of severe dehydrating diarrhea in infants and young children worldwide. **2. Analysis of Incorrect Options:** * **Retrovirus (e.g., HIV):** These possess a **diploid** genome (two identical copies of single-stranded RNA), but the genome itself is not segmented. * **Poliovirus:** A member of the **Picornaviridae** family, it has a single-stranded, positive-sense, **non-segmented** RNA genome. * **Rhabdovirus (e.g., Rabies):** This is a bullet-shaped virus with a single-stranded, negative-sense, **non-segmented** RNA genome. **3. NEET-PG High-Yield Clinical Pearls:** To remember the segmented RNA viruses, use the mnemonic **"BOAR"**: * **B**unyaviridae (3 segments) * **O**rthomyxoviridae (e.g., Influenza; 8 segments) * **A**renaviridae (2 segments) * **R**eoviridae (e.g., Rotavirus; 11 segments) **Key Fact:** Genetic reassortment in segmented viruses (especially Influenza) is the mechanism behind **Antigenic Shift**, which leads to pandemics. In contrast, **Antigenic Drift** (point mutations) occurs in both segmented and non-segmented viruses.

Q: Owl's eye appearance inclusion bodies can be demonstrated in the diagnosis of which human herpesvirus (HHV) infection?

HHV-5 (Cytomegalovirus). **Explanation:** The correct answer is **HHV-5 (Cytomegalovirus)**. **Why HHV-5 is correct:** Cytomegalovirus (CMV) infection is characterized by the formation of massive cellular enlargement (cytomegaly). The hallmark histopathological finding is the presence of large, **basophilic intranuclear inclusion bodies** surrounded by a clear halo, extending to the nuclear membrane. This specific morphology resembles an **"Owl’s eye."** These inclusions represent areas of active viral replication and are typically seen in epithelial cells of the renal tubules, bile ducts, or salivary glands. **Why other options are incorrect:** * **HHV-1 (Herpes Simplex Virus-1):** Characterized by **Cowdry Type A** inclusions (eosinophilic intranuclear inclusions) and multinucleated giant cells (Tzanck smear), but not the "Owl's eye" appearance. * **HHV-6 (Roseolovirus):** Primarily causes Roseola Infantum (Exanthem Subitum). While it infects T-cells, it does not produce the classic "Owl's eye" inclusions. * **HHV-4 (Epstein-Barr Virus):** Associated with infectious mononucleosis and various malignancies. The diagnostic hallmark is **atypical lymphocytes (Downey cells)** in the peripheral blood, not intranuclear inclusions. Note: "Owl's eye" nuclei are seen in Reed-Sternberg cells of Hodgkin Lymphoma (associated with EBV), but these are nucleoli, not viral inclusion bodies. **High-Yield Clinical Pearls for NEET-PG:** * **CMV** is the most common cause of congenital malformation (presents with periventricular calcifications and microcephaly). * In HIV patients, CMV is a major cause of **retinitis** ("pizza-pie" appearance) and **colitis**. * **Drug of choice:** Ganciclovir (Valganciclovir for prophylaxis). * **Culture:** CMV grows best in human fibroblast cell lines (demonstrating "shell vial" entry).

Q: Which of the following statements about hepatitis G virus is false?

It responds to lamivudine therapy.. **Explanation:** The Hepatitis G Virus (HGV), also known as **GB virus C (GBV-C)**, is a member of the *Flaviviridae* family. The correct answer is **D** because HGV is an **RNA virus**, and **Lamivudine** is a nucleoside analog that inhibits reverse transcriptase, primarily used for DNA viruses like Hepatitis B (HBV) or retroviruses like HIV. It has no therapeutic role in HGV infection. **Analysis of Options:** * **Option A:** HGV was independently discovered and named GB virus C (after surgeon G. Barker). Both terms are used interchangeably in medical literature. * **Option B:** It is a positive-sense, single-stranded **RNA virus**. Its primary mode of transmission is parenteral (blood-borne), similar to HCV and HBV. * **Option C:** Due to shared transmission routes (IV drug use, blood transfusions), HGV is frequently found as a co-infection with **HCV** (up to 10-20% of cases) and HIV. **High-Yield Clinical Pearls for NEET-PG:** 1. **Pathogenicity:** Despite its name, HGV is generally considered **non-pathogenic**. It does not cause acute or chronic hepatitis, nor does it worsen the clinical course of HCV or HBV. 2. **HIV Benefit:** A high-yield fact is that HGV/GBV-C co-infection in **HIV patients** is associated with **slower disease progression** and improved survival rates, possibly due to interference with HIV entry into CD4 cells. 3. **Diagnosis:** It is diagnosed via **RT-PCR** for HGV RNA; there is no routine serological test used in clinical practice.

Q: Which virus families possess double-stranded DNA in four different isomers?

Herpesviruses. **Explanation:** The correct answer is **Herpesviruses**. This is a high-yield molecular biology concept frequently tested in NEET-PG. **Why Herpesviruses?** The genome of Herpesviruses (such as HSV and CMV) consists of a linear, double-stranded DNA molecule. This genome is organized into two components: **Unique Long (UL)** and **Unique Short (US)** regions. Each of these regions is flanked by inverted repeat sequences. Because these segments can invert their orientation independently of one another, the genome can exist in **four different structural isomers** (topoisomers). This genomic flexibility is a hallmark of the *Herpesviridae* family. **Analysis of Incorrect Options:** * **Poxviruses (Option A):** While they are dsDNA viruses, their genome is a single, continuous linear molecule with covalently closed ends (hairpin loops). They do not undergo the specific segmental inversion required to form four isomers. * **Rabiesviruses (Option B):** These belong to the *Rhabdoviridae* family and possess a **negative-sense, single-stranded RNA (-ssRNA)** genome, not DNA. * **Orthomyxoviruses (Option D):** These (e.g., Influenza) possess a **segmented, negative-sense, single-stranded RNA** genome. While they have segments, they do not have dsDNA isomers. **High-Yield Clinical Pearls for NEET-PG:** * **Herpesvirus Structure:** They are the only viruses that possess an **envelope**, a **tegument** (space between capsid and envelope), and a dsDNA genome. * **Replication:** Unlike most DNA viruses that replicate in the nucleus, **Poxviruses** are the exception—they replicate in the **cytoplasm** because they carry their own DNA-dependent RNA polymerase. * **Isomer Significance:** The four isomers of Herpesviruses are functionally equivalent; all four are infectious and capable of producing progeny.

Question 1

Which of the following contains an RNA-dependent DNA polymerase as a structural component of the virion?

Accepted Answer

RNA tumor viruses

Answer

Adenoviruses

Answer

Orthomyxoviruses

Answer

Rhabdoviruses

Question 2

Evaluation of a specimen from a patient with hepatocellular carcinoma demonstrates the presence of a single-stranded RNA virus. Which of the following is the most probable etiological agent?

Accepted Answer

Hepatitis C virus

Answer

Hepatitis A virus

Answer

Hepatitis B virus

Answer

Hepatitis E virus

Question 3

Which of the following does not indicate Hepatitis B replication?

Accepted Answer

HBcAg

Answer

HBeAg

Answer

HBV DNA

Answer

Viral copies

Question 4

Reverse transcriptase sequence in HIV is best described as:

Accepted Answer

RNA - DNA - RNA

Answer

DNA - RNA

Answer

DNA - RNA - DNA

Answer

RNA - DNA

Question 5

Which of the following viruses is brick-shaped?

Accepted Answer

Small pox

Answer

Chicken pox

Answer

CMV

Answer

EBV

Question 6

Which of the following statement is TRUE about polio?

Accepted Answer

Increased muscular activity leads to increased paralysis

Answer

Paralytic polio is most common

Answer

Spastic paralysis

Answer

Polio vaccine is given orally

Question 7

Which virus has a segmented genome?

Accepted Answer

Rotavirus

Answer

Retrovirus

Answer

Poliovirus

Answer

Rhabdovirus

Question 8

Owl's eye appearance inclusion bodies can be demonstrated in the diagnosis of which human herpesvirus (HHV) infection?

Accepted Answer

HHV-5 (Cytomegalovirus)

Answer

HHV-1

Answer

HHV-6

Answer

HHV-4 (Epstein-Barr virus)

Question 9

Which of the following statements about hepatitis G virus is false?

Accepted Answer

It responds to lamivudine therapy.

Answer

It is also called GB virus.

Answer

It is a blood-borne RNA virus.

Answer

It is mostly found co-infecting with hepatitis C virus.

Question 10

Which virus families possess double-stranded DNA in four different isomers?

Accepted Answer

Herpesviruses

Answer

Poxviruses

Answer

Rabiesviruses

Answer

Orthomyxoviruses

Virology — MCQs

Virology — MCQs

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