NEET-PG 2018 Practice Questions

Q: Trilene is degraded by:

Cytochrome P450 oxidation. ***Cytochrome P450 oxidation*** - **Trichloroethylene (Trilene)** was historically used as an inhalational anesthetic and industrial solvent - In humans, it undergoes **hepatic metabolism primarily through cytochrome P450 enzymes**, particularly **CYP2E1** - The oxidation pathway produces metabolites including **chloral hydrate, trichloroethanol, and trichloroacetic acid** - This is a classic example of **Phase I detoxification** involving oxidative biotransformation - The metabolites are then conjugated (Phase II) or excreted renally *Glutathione conjugation* - While some chlorinated compounds undergo glutathione conjugation as a Phase II reaction - For trichloroethylene, **oxidation by CYP450 is the primary metabolic pathway**, not direct glutathione conjugation - GSH conjugation may occur with some metabolites but is not the main degradation route *Direct renal excretion* - Trilene is **lipophilic** and requires hepatic metabolism before elimination - Direct renal excretion without biotransformation is **minimal** - Metabolites (after oxidation) are excreted via kidneys *Acetylation* - **Acetylation** is a Phase II conjugation reaction typically for compounds with **amino or sulfonamide groups** - Trichloroethylene lacks the appropriate functional groups for acetylation - This pathway is **not involved** in Trilene metabolism

Q: Which of the following is an example of an X-linked disorder?

Color blindness. ***Color blindness*** - **Color blindness**, particularly red-green color blindness, is a classic example of an **X-linked recessive disorder**. - It results from mutations in genes encoding **photopigments** located on the X chromosome, affecting more males than females. - Represents one of the most commonly cited examples of X-linked inheritance in medical education. *Thalassemia* - **Thalassemia** is an **autosomal recessive disorder** affecting the synthesis of hemoglobin chains (α or β chains). - Not an X-linked condition; mutations are in genes on chromosome 16 (α-thalassemia) or chromosome 11 (β-thalassemia). - Commonly seen in populations from the Mediterranean, Middle East, and Asia. *Azoospermia* - **Azoospermia** (absence of sperm in ejaculate) is a clinical finding, not a specific genetic disorder. - Can result from various genetic causes including **Y-chromosome microdeletions** and **autosomal mutations** (e.g., CFTR gene in congenital bilateral absence of vas deferens). - Not classified as an X-linked disorder. *Sickle cell anemia* - **Sickle cell anemia** is an **autosomal recessive disorder** caused by a mutation in the β-globin gene on chromosome 11. - Results from substitution of valine for glutamic acid at position 6 of the β-globin chain (HbS). - Not an X-linked condition; both males and females are equally affected when inheriting two copies of the mutant allele.

Q: According to WHO classification, severe thinness is defined as a BMI below which value?

< 16. ***Correct: < 16 kg/m²*** - The WHO classifies **BMI < 16 kg/m²** as **severe thinness (Grade 3 thinness)** - This represents critically low body weight with significant health risks - Values like 12, 13, 14, or 15 all fall into this severe thinness category *18* - BMI **18.5-24.9 kg/m²** is classified as **normal/healthy weight** by WHO - BMI **17.0-18.49 kg/m²** is classified as **mild thinness (Grade 1)** - 18 is not the threshold for severe thinness *14* - 14 kg/m² is **an example of a value** that falls within severe thinness - However, the question asks for the **threshold/cutoff value**, which is **16 kg/m²** - Any BMI below 16 (including 14, 13, 12) indicates severe thinness *13* - Like option 14, this is **a value within** the severe thinness range - The **defining threshold** is **< 16 kg/m²**, not 13 - The question asks for the classification cutoff, not an example value within the range

Q: Acute Hemorrhagic Conjunctivitis is primarily caused by which type of Enterovirus?

Enterovirus type 70. ***Enterovirus type 70*** - **Enterovirus type 70** is the most common cause of **Acute Hemorrhagic Conjunctivitis (AHC)**, particularly in epidemic outbreaks. - AHC presents with rapid onset of **ocular pain**, **redness**, **swelling**, and **subconjunctival hemorrhages**. *Enterovirus type 68* - **Enterovirus D68 (EV-D68)** is primarily known for causing **respiratory illnesses**, ranging from mild to severe, and is associated with acute flaccid myelitis. - While it can cause respiratory symptoms, it is not a primary cause of **Acute Hemorrhagic Conjunctivitis**. *Enterovirus type 69* - **Enterovirus type 69** is a rare serotype and is not typically associated with specific human diseases or large-scale outbreaks. - Unlike EV70, it is not recognized as a significant cause of **conjunctivitis**. *Enterovirus type 71* - **Enterovirus A71 (EV-A71)** is a common cause of **hand, foot, and mouth disease (HFMD)**, especially in children, and can also lead to severe neurological complications. - While it causes various infections, it is not the primary cause of **hemorrhagic conjunctivitis**.

Q: Identify the organism related to the blood smear image.

Plasmodium falciparum. ***Plasmodium falciparum*** - The image clearly displays multiple **ring-form trophozoites** within red blood cells, some of which are *appliqué* or *accolade* forms (rings on the periphery of the red blood cell) and **multiple rings per red blood cell**, which are characteristic of *P. falciparum*. - Presence of **multiple parasites per red blood cell** and various developmental stages including occasional **banana-shaped gametocytes**, though not prominent in this specific field, are key indicators of *P. falciparum* infection, differentiating it from other malarial species. - *P. falciparum* is the most dangerous malarial species and can cause **cerebral malaria** and other severe complications. *Salmonella Typhi* - This bacterium causes **typhoid fever** and is typically identified through **blood culture** or serological tests (Widal test), not by direct visualization within red blood cells on a peripheral blood smear. - *Salmonella Typhi* is an **intracellular bacterium** that primarily infects phagocytic cells (macrophages), not erythrocytes, and does not present as ring forms or other parasitic stages in blood smears. *Toxoplasma gondii* - This parasite causes **toxoplasmosis** and is typically found as **tachyzoites** or **bradyzoites** (within cysts) in tissue samples or less commonly in macrophages in disseminated disease, but not as ring forms within red blood cells on a peripheral blood smear. - Diagnosis usually involves **serological testing** for IgM/IgG antibodies or PCR, as opposed to direct visualization of unique forms in blood smears. *Treponema pallidum* - This is the spirochete responsible for **syphilis** and is too small and thin (0.1-0.2 μm diameter) to be seen with standard light microscopy on routine blood smears. - It is best identified using **dark-field microscopy** or serological tests (VDRL, RPR, TPPA, FTA-ABS) and does not infect red blood cells in the manner shown.

Q: Best time to perform the quadruple test is:

15-20 weeks. ***15-20 weeks*** - The quadruple test measures levels of four substances (**alpha-fetoprotein**, **human chorionic gonadotropin**, **unconjugated estriol**, and **inhibin A**) in the mother's blood. - This window is optimal for detecting neural tube defects and chromosomal abnormalities like **Down syndrome** and **Trisomy 18**, allowing for timely counseling and further diagnostic testing if needed. *8-12 weeks* - This period is generally too early for the quadruple test to be accurate, as the levels of the markers would not be sufficiently distinct for reliable screening. - The **combined first-trimester screening** (nuchal translucency and blood tests for PAPP-A and hCG) is typically performed during this time. *11-15 weeks* - While some components might be detectable at the later end of this range, 15-20 weeks offers a more accurate window for all four markers of the quadruple test. - **Integrated screening**, which combines first and second-trimester markers, would involve blood draws around 10-14 weeks and then 15-20 weeks. *18-22 weeks* - This period is generally considered too late for optimal results of the quadruple test, as the fetal markers might be less indicative or diagnostic interventions options might be limited. - A **detailed ultrasound** for anatomical survey is usually performed around this time.

Q: What is meant by Superfecundation?

Fertilization of two or more ova in different intercourses in same menstrual cycle. ***Fertilization of two or more ova in different intercourses in same menstrual cycle*** - **Superfecundation** occurs when two or more ova released during the same menstrual cycle are fertilized by sperm from **separate acts of coitus**. - This can lead to **dizygotic twins** or multiples conceived at different times within a short window, potentially from different biological fathers. *Fertilization of two or more ova in one intercourse* - This scenario describes the fertilization of multiple ova within a **single sexual encounter**, often leading to **dizygotic multiples** but not superfecundation. - Superfecundation specifically implies fertilization from **separate instances of intercourse**. *Fertilization of ova and then its division* - This describes the formation of **monozygotic (identical) twins**, where a single fertilized ovum (zygote) later splits into two or more embryos. - It is distinct from superfecundation, which involves fertilization of **multiple ova**. *Fertilization of second ovum after first one is already implanted* - This describes **superfetation**, a rare phenomenon where a new pregnancy (fertilization and conception) occurs **while already pregnant** from a previous cycle. - Superfecundation, conversely, involves **multiple conceptions within the same menstrual cycle**, not across different cycles.

Q: What is the physiological response of the kidney during shock?

Renal blood flow decreases. ***Renal blood flow decreases*** - During shock, the **primary and most fundamental** physiological change affecting the kidney is a marked **reduction in renal blood flow (RBF)**. - Shock triggers intense **sympathetic activation** and **renin-angiotensin system (RAS) activation**, causing preferential **vasoconstriction** of renal vessels to redirect blood to vital organs (brain, heart). - RBF can drop to as low as **20-30% of normal** in severe shock, making this the hallmark renal response. - This reduction in RBF is the **upstream event** that triggers all other renal changes during shock. *Perfusion of kidney decreases* - While technically correct, "decreased perfusion" is **essentially synonymous** with decreased blood flow in this context. - The term "renal blood flow" is the **standard physiological terminology** used in medical literature to describe this phenomenon, making it the more precise answer. *Afferent arteriole resistance increases* - This is a **mechanism** by which RBF decreases, not the overall response itself. - Increased afferent arteriolar resistance is **secondary** to sympathetic activation and angiotensin II effects during shock. - It describes the "how" rather than the "what" of the kidney's response. *GFR decreases* - GFR reduction is a **consequence** of decreased RBF and increased afferent arteriolar resistance. - While clinically important (oliguria/acute kidney injury), it's a **downstream effect** rather than the primary physiological response. - The relationship: ↓RBF → ↓Glomerular hydrostatic pressure → ↓GFR

Q: Where will be the placement location for Auditory Brainstem Implant?

Recess of 4th ventricle. ***Recess of 4th ventricle*** - An **Auditory Brainstem Implant (ABI)** is placed on the **cochlear nucleus** in the brainstem, which is anatomically located near the **lateral recess of the fourth ventricle**. - The implant stimulates these nuclei directly, bypassing the damaged auditory nerve in patients who cannot benefit from cochlear implants. *Scala tympani* - The **scala tympani** is the location for electrode placement in a **cochlear implant**, not an auditory brainstem implant. - Cochlear implants stimulate the intact auditory nerve within the cochlea. *IAC* - The **internal auditory canal (IAC)** houses the auditory and facial nerves, but it is not the target site for an ABI. - The ABI is designed for patients whose auditory nerve (which passes through the IAC) is non-functional. *Back of ear* - The "back of the ear" is the general area where the **external processor of a cochlear implant** or a **bone-anchored hearing aid** is typically worn, not the surgical placement site for an ABI. - The ABI's internal component is surgically placed within the cranium.

Q: Which of the following is the preferred graft material for femoropopliteal bypass?

Reversed saphenous. ***Reversed saphenous*** - The **autologous reversed saphenous vein** is considered the **gold standard** for femoropopliteal bypass due to its superior patency rates and resistance to infection. - The vein's valves are bypassed by reversing its orientation, ensuring unidirectional blood flow. *Dacron* - **Dacron (polyethylene terephthalate)** grafts are synthetic and commonly used for large-diameter arterial bypasses, such as in the aorta, but have **inferior patency in infrainguinal bypasses** compared to autologous vein. - **Higher rates of thrombosis and infection** are observed with Dacron in smaller leg vessels due to compliance mismatch and increased anastomotic intimal hyperplasia. *PTFE* - **Polytetrafluoroethylene (PTFE)** grafts are synthetic and are an option when autologous vein is unavailable, particularly for above-knee femoropopliteal bypasses. - However, PTFE generally has **lower long-term patency rates** and a higher risk of complications like **graft thrombosis and infection** compared to autologous vein grafts. *None of the options* - This option is incorrect because the **reversed saphenous vein** is indeed a preferred and highly effective graft material for femoropopliteal bypass. - The clinical evidence strongly supports its use over synthetic alternatives when available.

Question 1

Trilene is degraded by:

Accepted Answer

Cytochrome P450 oxidation

Answer

Glutathione conjugation

Answer

Direct renal excretion

Answer

Acetylation

Question 2

Which of the following is an example of an X-linked disorder?

Accepted Answer

Color blindness

Answer

Thalassemia

Answer

Azoospermia

Answer

Sickle cell anemia

Question 3

According to WHO classification, severe thinness is defined as a BMI below which value?

Accepted Answer

< 16

Answer

18

Answer

14

Answer

13

Question 4

Acute Hemorrhagic Conjunctivitis is primarily caused by which type of Enterovirus?

Accepted Answer

Enterovirus type 70

Answer

Enterovirus type 68

Answer

Enterovirus type 69

Answer

Enterovirus type 71

Question 5

Identify the organism related to the blood smear image.

Accepted Answer

Plasmodium falciparum

Answer

Salmonella Typhi

Answer

Toxoplasma gondii

Answer

Treponema pallidum

Question 6

Best time to perform the quadruple test is:

Accepted Answer

15-20 weeks

Answer

8-12 weeks

Answer

11-15 weeks

Answer

18-22 weeks

Question 7

What is meant by Superfecundation?

Accepted Answer

Fertilization of two or more ova in different intercourses in same menstrual cycle

Answer

Fertilization of ova and then its division

Answer

Fertilization of two or more ova in one intercourse

Answer

Fertilization of second ovum after first one is already implanted

Question 8

What is the physiological response of the kidney during shock?

Accepted Answer

Renal blood flow decreases

Answer

GFR decreases

Answer

Perfusion of kidney decreases

Answer

Afferent arteriole resistance increases

Question 9

Where will be the placement location for Auditory Brainstem Implant?

Accepted Answer

Recess of 4th ventricle

Answer

Scala tympani

Answer

IAC

Answer

Back of ear

Question 10

Which of the following is the preferred graft material for femoropopliteal bypass?

Accepted Answer

Reversed saphenous

Answer

PTFE

Answer

Dacron

Answer

None of the options

NEET-PG 2018

Biochemistry

Community Medicine

Microbiology

Obstetrics and Gynecology

Physiology

Surgery