NEET-PG 2013 Practice Questions

Q: What is the number of variable regions present on each light and heavy chain of an antibody?

1. ***1*** - Each **light chain** and **heavy chain** within an antibody molecule contains **one variable region (V domain)**. - These variable regions are crucial for **antigen binding specificity**, as they combine to form the antigen-binding site. - The variable domain is located at the **N-terminal end** of each chain. *2* - While a complete antibody molecule has **two antigen-binding sites** (bivalent), each formed by pairing of VH and VL domains, individual chains possess only **one variable region each**. - The number '2' refers to the total number of identical binding sites on the intact antibody, not the number of variable regions per chain. *3* - The number **3** does not correspond to the number of variable regions on individual chains. - This might be confused with the **three complementarity-determining regions (CDRs)** present within each variable domain (CDR1, CDR2, CDR3), which are hypervariable loops that directly contact the antigen. *4* - The number **4** is incorrect for variable regions. - This number corresponds to the total number of **polypeptide chains** in a complete IgG antibody (2 heavy + 2 light chains), or the number of **constant domains** in some heavy chain isotypes (IgM, IgE have 4 CH domains).

Q: What was the target reduction in child mortality rates set by the Millennium Development Goals (MDGs) between 1990 and 2015?

Two-thirds. ***Two-thirds*** - The **Millennium Development Goal 4 (MDG 4)** specifically aimed to **reduce child mortality by two-thirds** among children under five years old between 1990 and 2015. - This target focused on improving maternal and child health outcomes globally. *Half* - Reducing child mortality by half was not the specific target set by MDG 4 for the 1990-2015 period. - While improvements were sought, the ambition was a more substantial reduction. *One-fourth* - A reduction of one-fourth would have been a significantly lower target than what was ultimately set and pursued by the MDGs. - The goals were designed to be ambitious yet achievable. *One-third* - Reducing child mortality by one-third falls short of the actual target established by the MDGs. - The international community aimed for a greater impact on child survival rates.

Q: According to which section of the Indian Penal Code (IPC) is the punishment for murder prescribed?

Sec 302 IPC. ***Sec 302 IPC*** - This section of the Indian Penal Code explicitly prescribes the **punishment for murder**, which can include death or life imprisonment. - While other sections define murder or deal with related offenses, Section 302 specifically addresses the **consequences** for committing murder. *Sec 301 IPC* - This section deals with **culpable homicide by causing death of person other than person whose death was intended**. - It specifies that if a person commits culpable homicide intending to cause the death of one person, but instead causes the death of another, they should be punished as if they had caused the death of the person they intended to kill. *Sec 300 IPC* - This section defines what constitutes **murder** under the Indian Penal Code. - It outlines the specific circumstances and intentions that elevate culpable homicide to the offense of murder. *Sec 304 IPC* - This section prescribes the **punishment for culpable homicide not amounting to murder**. - It specifies different levels of punishment based on the intention or knowledge of the offender, distinguishing it from murder.

Q: Which of the following is a saccharolytic species of Clostridium?

Clostridium septicum. ***Clostridium septicum*** - *Clostridium septicum* is a **saccharolytic** species, meaning it ferments carbohydrates to produce gas, which contributes to the rapid tissue destruction seen in **gas gangrene**. - Its ability to rapidly consume sugars in tissues fuels its invasive growth and toxin production, which is characteristic of its pathogenic mechanism. *Clostridium tetani* - *Clostridium tetani* is a **proteolytic** species, primarily deriving its energy from **protein degradation**. - It does not ferment carbohydrates, and its pathogenicity is mainly due to the production of **tetanospasmin**, a neurotoxin. *Clostridium cochlearium* - *Clostridium cochlearium* is a **proteolytic** species that metabolizes proteins and amino acids. - It is not known for significant saccharolytic activity and is typically found in environments rich in protein. *None of the options* - This option is incorrect because *Clostridium septicum* is indeed a saccharolytic species, as detailed above.

Q: JSB stain is used for which parasite?

Filaria. ***Filaria*** - The **JSB stain (Jaswant Singh Battacharya stain)** is a rapid Romanowsky-type stain specifically developed for the diagnosis of **microfilariae** in blood films. - It allows for clear visualization of the sheaths and nuclei of microfilariae, which is crucial for species identification and diagnosis of **filariasis**. *Malaria* - **Giemsa stain** is the gold standard for identifying malaria parasites in thick and thin blood smears, not JSB stain. - Giemsa allows for detailed morphological differentiation of malaria species and stages within **red blood cells**. *Kala azar* - **Kala-azar (visceral leishmaniasis)** is diagnosed by detecting **Leishman bodies (amastigotes)** in bone marrow, splenic, or lymph node aspirates. - Stains like **Giemsa** or **Leishman stain** are traditionally used for visualizing these amastigotes. *Sleeping sickness* - **Sleeping sickness (African trypanosomiasis)** is diagnosed by identifying **trypomastigotes** in blood smears, lymph node aspirates, or cerebrospinal fluid. - **Giemsa stain** is commonly used for the microscopic examination of these specimens to detect the parasites.

Q: Which of the following bacteria does not exhibit bipolar staining?

Haemophilus influenzae. ***Haemophilus influenzae*** - *Haemophilus influenzae* is a **pleomorphic coccobacillus** that typically stains uniformly and does not exhibit characteristic **bipolar staining**. - Its presence is often identified by Gram stain showing small, Gram-negative rods, but without the distinctive safety pin appearance. *Calymmatobacterium granulomatis* - *Calymmatobacterium granulomatis* (now *Klebsiella granulomatis*) is known to exhibit **bipolar staining**, often described as a **"safety pin" appearance**, especially in tissue smears from granuloma inguinale lesions. - This characteristic staining is due to the concentration of stain at the ends of the rod-shaped bacteria. *Yersinia pestis* - *Yersinia pestis*, the causative agent of plague, is classically described as having **bipolar staining**, giving it a distinctive **"safety pin" appearance** under a microscope. - This finding is a key diagnostic feature, particularly when observed in Gram-stained smears of clinical samples. *Francisella tularensis* - *Francisella tularensis* is a small, Gram-negative coccobacillus that is known to exhibit **bipolar staining**, though it may be less prominent than in *Yersinia pestis*. - This characteristic can assist in the microscopic identification of the bacterium, which causes tularemia.

Q: Macrophage tropic strains of HIV use which co-receptor?

CCR5. ***CCR5*** - **Macrophage-tropic** HIV strains, also known as **R5 strains**, primarily use the **CCR5 co-receptor** to enter target cells. - These strains are typically involved in the **initial infection** and transmission of HIV. - CCR5-tropic viruses are usually the **predominant strains transmitted** during sexual transmission. *CXCR4* - **T-cell-tropic** HIV strains, or **X4 strains**, preferentially utilize the **CXCR4 co-receptor** for cell entry. - These strains are associated with a **more rapid decline in CD4+ T-cell counts** during later stages of HIV infection. - Emergence of X4 strains is linked to **disease progression**. *CCR3* - While a chemokine receptor, **CCR3** is not a primary co-receptor used by common HIV strains for entry into macrophages or T cells. - CCR3 is primarily involved in **eosinophil chemotaxis** and allergic responses. *CCR2* - **CCR2** is another chemokine receptor but is **not a major co-receptor** for HIV entry. - While some laboratory-adapted strains may show minor usage, it is not clinically significant for macrophage-tropic HIV strains.

Q: Botulinum toxin acts on

Synapse. ***Synapse*** - **Botulinum toxin** acts by inhibiting the release of **acetylcholine** at the **neuromuscular junction**, which is a type of synapse. - This blockade of neurotransmitter release at the **presynaptic terminal** prevents muscle contraction, leading to paralysis. *Smooth muscle of intestine* - While botulinum toxin can affect smooth muscle indirectly by paralyzing the motor nerves innervating them, its primary site of action is the **synapse** itself, not directly on the muscle fibers. - The toxin primarily targets the nerve endings, rather than the mechanical contractility of the muscle cell. *Central nervous system* - **Botulinum toxin** does not readily cross the **blood-brain barrier**, meaning its primary effects are peripheral. - Its therapeutic and toxic effects are localized to the **peripheral nervous system** and neuromuscular junctions. *Sensory nerves* - **Botulinum toxin** specifically targets **motor nerve endings** to inhibit acetylcholine release, leading to muscle paralysis. - It does not directly affect the function of **sensory nerve transmission** or pain perception in the same way.

Q: Gynaecomastia is caused by which drug?

Spironolactone. ***Spironolactone*** - Spironolactone is a **well-established cause of gynaecomastia**, occurring in 5-10% of patients in a dose-dependent manner. - It acts as an **anti-androgen** by blocking androgen receptors and inhibiting testosterone synthesis, thereby increasing the estrogen to androgen ratio. - It is a **potassium-sparing diuretic** and aldosterone antagonist, commonly used in heart failure, hypertension, and conditions requiring androgen blockade. *Rifampicin* - Rifampicin is an **antibiotic** primarily used to treat tuberculosis and acts as a **strong inducer of cytochrome P450 enzymes**. - While rare hormonal effects have been reported, it is **not a recognized common cause** of gynaecomastia. - Main side effects include hepatotoxicity, orange discoloration of bodily fluids, and drug interactions. *Thiazide* - Thiazide diuretics work by inhibiting the **sodium-chloride cotransporter** in the distal convoluted tubule. - They are **not commonly associated** with gynaecomastia; typical side effects include hypokalemia, hyponatremia, and hyperglycemia. *Propranolol* - Propranolol is a **non-selective beta-blocker** used for hypertension, angina, arrhythmias, and anxiety. - While beta-blockers have rarely been implicated, propranolol is **not a well-established cause** of gynaecomastia compared to spironolactone. - Common side effects include bradycardia, fatigue, and bronchospasm.

Q: Which anticancer drug is known to inhibit spindle formation during cell division?

Vinca alkaloids. ***Vinca alkaloids*** - **Vinca alkaloids**, such as **vincristine** and **vinblastine**, bind to **tubulin** and prevent its polymerization into microtubules. - This action effectively **inhibits the formation of the mitotic spindle**, leading to metaphase arrest and ultimately cell death. *Busulfan* - **Busulfan** is an **alkylating agent** that **cross-links DNA**, thereby interfering with DNA replication and transcription. - Its primary mechanism is **DNA damage**, not direct inhibition of spindle formation. *5-FU* - **5-fluorouracil (5-FU)** is an **antimetabolite** that inhibits **thymidylate synthase**, thereby impairing DNA synthesis and repair. - It acts by **mimicking pyrimidine bases** and incorporating into DNA and RNA, leading to cellular dysfunction. *Methotrexate* - **Methotrexate** is an **antifolate** drug that inhibits **dihydrofolate reductase**, an enzyme crucial for the synthesis of purines and pyrimidines. - This enzyme inhibition leads to **impaired DNA and RNA synthesis**, impacting rapidly dividing cells.

Question 1

What is the number of variable regions present on each light and heavy chain of an antibody?

Accepted Answer

1

Answer

2

Answer

3

Answer

4

Question 2

What was the target reduction in child mortality rates set by the Millennium Development Goals (MDGs) between 1990 and 2015?

Accepted Answer

Two-thirds

Answer

Half

Answer

One-fourth

Answer

One-third

Question 3

According to which section of the Indian Penal Code (IPC) is the punishment for murder prescribed?

Accepted Answer

Sec 302 IPC

Answer

Sec 301 IPC

Answer

Sec 300 IPC

Answer

Sec 304 IPC

Question 4

Which of the following is a saccharolytic species of Clostridium?

Accepted Answer

Clostridium septicum

Answer

Clostridium tetani

Answer

Clostridium cochlearium

Answer

None of the options

Question 5

JSB stain is used for which parasite?

Accepted Answer

Filaria

Answer

Kala azar

Answer

Sleeping sickness

Answer

Malaria

Question 6

Which of the following bacteria does not exhibit bipolar staining?

Accepted Answer

Haemophilus influenzae

Answer

Yersinia pestis

Answer

Calymmatobacterium granulomatis

Answer

Francisella tularensis

Question 7

Macrophage tropic strains of HIV use which co-receptor?

Accepted Answer

CCR5

Answer

CXCR4

Answer

CCR3

Answer

CCR2

Question 8

Botulinum toxin acts on

Accepted Answer

Synapse

Answer

Smooth muscle of intestine

Answer

Central nervous system

Answer

Sensory nerves

Question 9

Gynaecomastia is caused by which drug?

Accepted Answer

Spironolactone

Answer

Rifampicin

Answer

Thiazide

Answer

Propranolol

Question 10

Which anticancer drug is known to inhibit spindle formation during cell division?

Accepted Answer

Vinca alkaloids

Answer

Busulfan

Answer

5-FU

Answer

Methotrexate

NEET-PG 2013

Biochemistry

Community Medicine

Forensic Medicine

Microbiology

Pharmacology