Virology Practice Questions

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 organism causes cervical carcinoma?

Human Papillomavirus (HPV). **Explanation:** **Human Papillomavirus (HPV)** is the primary etiological agent of cervical carcinoma. The oncogenic potential lies in high-risk strains (primarily **HPV 16 and 18**), which integrate their DNA into the host genome. This leads to the overexpression of two key oncoproteins: **E6**, which degrades the **p53** tumor suppressor protein, and **E7**, which inactivates the **Retinoblastoma (Rb)** protein. The loss of these cell cycle checkpoints results in unregulated cellular proliferation and malignant transformation. **Analysis of Incorrect Options:** * **Hepatitis A Virus (HAV):** An RNA virus transmitted via the fecal-oral route. It causes acute hepatitis but is never associated with chronic infection or oncogenesis. * **Hepatitis B Virus (HBV) & Hepatitis C Virus (HCV):** While both are strongly associated with carcinogenesis, they specifically cause **Hepatocellular Carcinoma (HCC)**, not cervical cancer. HBV is a DNA virus that integrates into the host genome, while HCV is an RNA virus that causes cancer primarily through chronic inflammation and cirrhosis. **High-Yield Clinical Pearls for NEET-PG:** * **High-risk HPV types:** 16, 18 (cause ~70% of cases), 31, and 33. * **Low-risk HPV types:** 6 and 11 (cause Genital Warts/Condyloma Acuminata). * **Screening:** Pap smear looks for **Koilocytes** (cells with perinuclear halo and wrinkled "raisinoid" nuclei). * **Vaccination:** The Quadrivalent vaccine (Gardasil) targets types 6, 11, 16, and 18. The most effective time for administration is before the first sexual exposure (ages 9–14).

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: Which of the following methods is adopted for screening HIV infection?

ELISA followed by western blot technique. The standard diagnostic algorithm for HIV follows a two-step approach designed to maximize both sensitivity and specificity. **1. Why Option C is Correct:** * **ELISA (Screening):** The first step is an Enzyme-Linked Immunosorbent Assay (ELISA). It is highly **sensitive**, meaning it is excellent at detecting even minute amounts of antibodies/antigens to ensure no positive cases are missed. However, it can occasionally yield false positives. * **Western Blot (Confirmatory):** If the ELISA is reactive, a Western Blot is performed. This test is highly **specific** as it detects antibodies against specific viral proteins (like gp120, gp41, and p24). It confirms the diagnosis and eliminates false positives from the screening stage. **2. Why Other Options are Incorrect:** * **Option A (Virus Isolation):** Culturing HIV is technically demanding, expensive, and time-consuming. It is used in research settings, not for routine screening. * **Option B:** This reverses the logical order. We do not use a complex, expensive confirmatory test before a simple screening test. * **Option D (PCR):** While highly sensitive, PCR (DNA/RNA detection) is primarily used for diagnosing HIV in infants (where maternal antibodies interfere with ELISA), window period detection, or monitoring viral load. It is not the standard population screening tool. **High-Yield Clinical Pearls for NEET-PG:** * **Window Period:** The time between infection and the appearance of detectable antibodies (usually 2–8 weeks). * **4th Generation ELISA:** Now the "Gold Standard" screening tool; it detects both **p24 antigen** and **HIV-1/2 antibodies**, significantly shortening the window period. * **Diagnosis in Infants:** PCR is the investigation of choice for babies born to HIV-positive mothers up to 18 months of age.

Q: Which of the following viruses is known to cause latency?

All of the above. **Explanation:** Viral latency is a phase in certain viral life cycles where, after initial infection, the virus remains dormant within host cells without active replication. During this period, the viral genome is maintained (either as an episome or integrated into host DNA), allowing the virus to evade the immune system and reactivate later. * **Herpes Simplex Virus Type II (HSV-II):** As a member of the *Alphaherpesvirinae* subfamily, HSV-II establishes lifelong latency in the **sacral sensory nerve ganglia**. Reactivation typically results in recurrent genital herpes. * **Cytomegalovirus (CMV):** A member of the *Betaherpesvirinae* subfamily, CMV establishes latency in **mononuclear cells** (monocytes, lymphocytes) and myeloid progenitor cells in the bone marrow. * **Human Immunodeficiency Virus (HIV):** HIV is a retrovirus that integrates its DNA (provirus) into the host genome. It establishes a "latent reservoir" primarily in **resting CD4+ T cells**. This latency is the primary reason why current ART (Antiretroviral Therapy) cannot fully eradicate the virus. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Latency:** * **HSV-1:** Trigeminal ganglia. * **Varicella-Zoster Virus (VZV):** Dorsal root ganglia. * **Epstein-Barr Virus (EBV):** B-lymphocytes. * **Mechanism:** Herpesviruses maintain their genome as circular episomes, whereas HIV integrates into the host chromosome. * **Reactivation:** Often triggered by immunosuppression, stress, or fever. In HIV, "shock and kill" is a researched strategy to flush the virus out of its latent state.

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 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 viruses is brick-shaped?

Accepted Answer

Small pox

Answer

Chicken pox

Answer

CMV

Answer

EBV

Question 2

Which organism causes cervical carcinoma?

Accepted Answer

Human Papillomavirus (HPV)

Answer

Hepatitis A Virus (HAV)

Answer

Hepatitis B Virus (HBV)

Answer

Hepatitis C Virus (HCV)

Question 3

One virus particle prevents the multiplication of a second virus. This phenomenon is known as:

Accepted Answer

Viral interference

Answer

Mutation

Answer

Superinfection

Answer

Permutation

Question 4

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 5

Which of the following viruses commonly cause gastroenteritis?

Accepted Answer

Enterovirus

Answer

Rotavirus

Answer

Norwalk virus

Answer

Adenovirus

Question 6

Which virus has a segmented genome?

Accepted Answer

Rotavirus

Answer

Retrovirus

Answer

Poliovirus

Answer

Rhabdovirus

Question 7

Which of the following methods is adopted for screening HIV infection?

Accepted Answer

ELISA followed by western blot technique

Answer

Virus isolation

Answer

Western blot followed by ELISA

Answer

Polymerase chain reaction

Question 8

Which of the following viruses is known to cause latency?

Accepted Answer

All of the above

Answer

Herpes Simplex Virus Type II (HSV-II)

Answer

Cytomegalovirus (CMV)

Answer

Human Immunodeficiency Virus (HIV)

Question 9

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 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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