Biochemistry
2 questionsWhat is the first purine nucleotide synthesized in de novo purine biosynthesis?
What are Okazaki fragments?
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 351: What is the first purine nucleotide synthesized in de novo purine biosynthesis?
- A. AMP
- B. GMP
- C. IMP (Correct Answer)
- D. UMP
Explanation: ***IMP (Inosine Monophosphate)*** - **IMP** is the first complete purine nucleotide synthesized during the **de novo purine biosynthesis pathway**. - It serves as a branch point, from which **AMP** and **GMP** are subsequently synthesized through separate pathways. *AMP (Adenosine Monophosphate)* - **AMP** is a derivative of **IMP**, synthesized by the addition of an amino group from **aspartate** to IMP. - This step occurs after the formation of the complete purine ring structure in IMP. *GMP (Guanosine Monophosphate)* - **GMP** is also derived from **IMP**, through a pathway involving the oxidation of IMP to **XMP** (xanthosine monophosphate) and subsequent amination. - Its synthesis occurs downstream from IMP. *UMP (Uridine Monophosphate)* - **UMP** is a **pyrimidine nucleotide**, not a purine, and is synthesized via a completely different de novo pathway. - Pyrimidine biosynthesis involves forming the ring structure first, then attaching it to ribose-phosphate, unlike purine synthesis which builds the ring on a pre-existing ribose-phosphate.
Question 352: What are Okazaki fragments?
- A. Long pieces of DNA on the lagging strand.
- B. Short pieces of DNA on the lagging strand. (Correct Answer)
- C. Short pieces of DNA on the leading strand.
- D. Long pieces of DNA on the leading strand.
Explanation: ***Short pieces of DNA on the lagging strand.*** - **Okazaki fragments** are the short, newly synthesized DNA fragments that are formed on the **lagging strand** during DNA replication. - The lagging strand is synthesized discontinuously because DNA polymerase can only add nucleotides in the **5' to 3' direction**, requiring it to move away from the replication fork as the DNA unwinds. *Long pieces of DNA on the lagging strand.* - The lagging strand is synthesized discontinuously in **short fragments**, not long continuous pieces. - The enzyme **DNA ligase** eventually joins these short fragments together to form a continuous strand. *Short pieces of DNA on the leading strand.* - The **leading strand** is synthesized continuously in one long stretch, moving towards the replication fork. - It does not require the synthesis of short fragments like the lagging strand. *Long pieces of DNA on the leading strand.* - While the leading strand is synthesized in a continuous, long piece, this statement does not accurately describe Okazaki fragments, which are specific to the lagging strand. - The leading strand's continuous synthesis is due to its **3' to 5' template orientation**, allowing DNA polymerase to proceed uninterrupted.
Internal Medicine
3 questionsWhich of the following is not a feature of Poststreptococcal Glomerulonephritis (PSGN)?
In which condition is Tau protein primarily implicated?
In which condition is the Doll's Eye Reflex tested?
NEET-PG 2015 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 351: Which of the following is not a feature of Poststreptococcal Glomerulonephritis (PSGN)?
- A. HTN
- B. Increased urea
- C. Increased creatinine
- D. Normal C3 level (Correct Answer)
Explanation: ***Normal C3 level*** - In Post-streptococcal glomerulonephritis (PSGN), **C3 levels are typically decreased** due to complement consumption during the inflammatory process. [1] - A **normal C3 level** would not be consistent with PSGN, as it suggests no significant complement activation. *Increased urea* - Increased urea can occur due to **impaired renal function**, which is common in PSGN due to glomerular inflammation. [1] - It's a typical finding reflecting the kidneys' inability to excrete waste products properly. *HTN* - Hypertension is frequently associated with PSGN due to **volume overload** and activation of the renin-angiotensin system. [1] [2] - It is a common clinical feature that results from increased fluid retention. *Increased creatinine* - Increased creatinine levels indicate **renal impairment**, which is characteristic of PSGN as kidney function is affected during this condition. [1] - This finding highlights the reduction in glomerular filtration rate (GFR), typical in glomerulonephritis. [2]
Question 352: In which condition is Tau protein primarily implicated?
- A. Lewy body dementia
- B. Picks disease (Correct Answer)
- C. Amyloidosis
- D. Alzheimer's disease
Explanation: Pick's disease - Pick's disease is a **frontotemporal dementia** characterized by aggregates of **hyperphosphorylated tau protein** within neurons, forming **Pick bodies**. - These tau inclusions lead to neuronal degeneration, particularly in the **frontal and temporal lobes**, causing distinct behavioral and language deficits. *Alzheimer's disease* - While **tau protein** is implicated in Alzheimer's disease through the formation of **neurofibrillary tangles**, the primary protein is **beta-amyloid**, which forms plaques [1]. - Alzheimer's disease typically presents with **memory loss** as the predominant initial symptom, unlike Pick's disease [1]. *Lewy body dementia* - Lewy body dementia is primarily characterized by the aggregation of **alpha-synuclein protein** into Lewy bodies within neurons. - While tau pathology can sometimes co-exist, it is not the **primary diagnostic hallmark** of this condition. *Amyloidosis* - Amyloidosis refers to a group of diseases characterized by the abnormal extracellular deposition of **insoluble fibrillar proteins** called amyloids. - The amyloid protein can be derived from various precursors, such as **amyloid light chains** or **serum amyloid A**, which is distinct from tau.
Question 353: In which condition is the Doll's Eye Reflex tested?
- A. Hemiplegic
- B. Paraplegic
- C. Cerebral palsy
- D. Unconscious patients (Correct Answer)
Explanation: ***Unconscious patients*** - The **Doll's Eye Reflex**, also known as the **oculocephalic reflex**, is a brainstem reflex used to assess brainstem function in **comatose or unconscious patients** [1]. - It is positive if the eyes move in the opposite direction to the head turn, indicating intact brainstem pathways [1]. *Hemiplegic* - **Hemiplegia** refers to paralysis on one side of the body, often due to stroke or brain injury. - While it can be associated with altered consciousness, the Doll's Eye Reflex specifically tests brainstem integrity in unconscious states, not the motor deficits of hemiplegia itself. *Paraplegic* - **Paraplegia** is paralysis affecting the lower half of the body. - This condition primarily involves spinal cord damage and does not directly relate to the assessment of brainstem function using the Doll's Eye Reflex. *Cerebral palsy* - **Cerebral palsy** is a group of disorders affecting movement, muscle tone, or posture, caused by damage to the developing brain. - While individuals with cerebral palsy may have neurological impairments, the Doll's Eye Reflex is not a primary diagnostic or assessment tool for this chronic condition; it is used acutely in unconscious states.
Pathology
4 questionsWhat is the most common nephropathy associated with malignancy?
Irregular scarred kidney with pelvic dilatation is seen with?
Which chromosomal translocation is associated with follicular thyroid carcinoma?
Sezary cells show which type of nucleus?
NEET-PG 2015 - Pathology NEET-PG Practice Questions and MCQs
Question 351: What is the most common nephropathy associated with malignancy?
- A. Focal segmental glomerulosclerosis (FSGS)
- B. Minimal change disease
- C. IgA nephropathy
- D. Membranous glomerulonephritis (Correct Answer)
Explanation: ***Membranous glomerulonephritis*** - **Membranous glomerulonephritis** has the strongest and most frequent association with solid organ malignancies, particularly in older patients. - While other glomerulopathies can be linked to cancer, **membranous nephropathy** is the most common paraneoplastic glomerulopathy in adults. *Focal segmental glomerulosclerosis (FSGS)* - While FSGS can be associated with certain cancers, particularly hematological malignancies and HIV-associated nephropathy, it is **less common** than membranous nephropathy in solid tumors. - The link is often with **HIV-associated nephropathy** or direct tumor effects rather than a paraneoplastic syndrome. *Minimal change disease* - Minimal change disease is predominantly seen in **children** and is less frequently associated with malignancy compared to membranous nephropathy. - When associated with malignancy, it is typically with **lymphoproliferative disorders** like Hodgkin lymphoma. *IgA nephropathy* - **IgA nephropathy** is the most common primary glomerulonephritis worldwide but has a **weak and inconsistent association** with malignancy. - Its presence alongside cancer is often coincidental rather than directly causative.
Question 352: Irregular scarred kidney with pelvic dilatation is seen with?
- A. Chronic pyelonephritis (Correct Answer)
- B. Polycystic kidney
- C. Renal artery stenosis
- D. Tuberculosis of kidney
Explanation: ***Chronic pyelonephritis*** - Characterized by irregular scarring of the kidney and often leads to **pelvic dilatation** due to recurrent infections and obstruction [1]. - The damage from inflammation results in **cortical scarring** and can affect kidney function significantly over time [1]. *Renal artery stenosis* - Typically presents with **hypertension** and may lead to ischemic atrophy, but does not cause significant **pelvic dilatation**. - The kidney appears small and often asymmetric, but not typically irregular and scarred. *Tuberculosis of kidney* - Can cause damage to the kidney, but usually leads to **caseating granulomas** and can cause abscesses, not specifically irregular scarring with pelvic dilation. - Often presents with systemic symptoms such as fever and night sweats, along with hematuria. *Polycystic kidney* - Characterized by multiple cysts in both kidneys leading to enlarged kidneys, but does not typically present as **irregularly scarred kidneys**. - Usually associated with **hemodynamic issues** and hypertension but not pelvic dilatation in the sense of scarring or fibrosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 937-939.
Question 353: Which chromosomal translocation is associated with follicular thyroid carcinoma?
- A. PAX8 - PPARγ (Correct Answer)
- B. ALK - NPM1
- C. ETV6 - NTRK3
- D. RET - PTC1
Explanation: ***PAX8 - PPARγ*** - The **PAX8-PPARγ fusion oncogene** is a well-established molecular marker directly associated with **follicular thyroid carcinoma (FTC)**. - This translocation leads to the expression of a fusion protein that contributes to **thyroid cell proliferation** and **tumorigenesis**. *ALK - NPM1* - The **ALK-NPM1 fusion** is primarily observed in some types of **anaplastic large cell lymphoma**, not thyroid cancers. - This translocation typically results in an **activated anaplastic lymphoma kinase (ALK)**, driving lymphoproliferation. *ETV6 - NTRK3* - The **ETV6-NTRK3 rearrangement** is characteristic of **secretory carcinoma** (formerly mammary analogue secretory carcinoma), often affecting salivary glands, and is not a common finding in thyroid malignancies. - This fusion leads to the activation of the **NTRK3 receptor tyrosine kinase**, involved in cell growth and survival. *RET - PTC1* - The **RET-PTC1 rearrangement (RET/papillary thyroid carcinoma 1)** is specifically associated with **papillary thyroid carcinoma (PTC)**, which is histologically distinct from follicular thyroid carcinoma. - This fusion activates the **RET proto-oncogene**, promoting cell proliferation and survival in papillary thyroid cancer.
Question 354: Sezary cells show which type of nucleus?
- A. Cerebriform (Correct Answer)
- B. Pleomorphic
- C. Round
- D. Eosinophilic
Explanation: ***Cerebriform*** - **Sezary cells** are characterized by their distinctive **cerebriform nuclei**, giving them an irregular, convoluted appearance [1,2]. - This finding is a hallmark of **cutaneous T-cell lymphoma** and emphasizes their potential malignancy [1,2]. *Round* - Round nuclei do not reflect the typical morphology of **Sezary cells**, which are noted for their **irregular shape**. - Other lymphocytes may exhibit round nuclei, but this does not specifically indicate a **Sezary cell** presence. *Pleomorphic* - While some malignant cells might show **pleomorphic nuclei**, Sezary cells uniquely showcase **cerebriform nuclei** rather than varying shapes [1,2]. - Pleomorphic is not a defining characteristic of **Sezary cells**, making this description inaccurate. *Eosinophillic* - Eosinophilic refers to cells that stain positively for **eosin**, typically associated with **eosinophils**, which is not relevant to **Sezary cells**. - Sezary cells are more about their **nuclear morphology** and less about eosinophilic staining characteristics. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 564-565. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 613-614.
Physiology
1 questionsWhich part of the sympathetic nervous system is responsible for secreting catecholamines?
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 351: Which part of the sympathetic nervous system is responsible for secreting catecholamines?
- A. Cardiac ganglion
- B. Cervical sympathetic chain
- C. Adrenal medulla (Correct Answer)
- D. Thoracic sympathetic chain
Explanation: ***Adrenal medulla*** - The adrenal medulla acts as a modified **sympathetic ganglion**, directly innervated by **preganglionic sympathetic fibers**. - Upon stimulation, it releases a high concentration of **epinephrine** (adrenaline) and a smaller amount of **norepinephrine** (noradrenaline) into the bloodstream, acting as hormones. *Cardiac ganglion* - **Cardiac ganglia** are parasympathetic ganglia located in the heart, involved in regulating heart rate and contractility via acetylcholine release. - They do not secrete **catecholamines** but rather act as relay stations for parasympathetic innervation. *Cervical sympathetic chain* - The **cervical sympathetic chain** primarily innervates structures in the head, neck, and upper limbs, influencing functions like pupils, salivary glands, and sweat glands. - While it contains sympathetic neurons, its primary role is not the systemic release of **catecholamines** into the bloodstream. *Thoracic sympathetic chain* - The **thoracic sympathetic chain** provides sympathetic innervation to organs in the thoracic and abdominal cavities, influencing heart rate, bronchodilation, and visceral blood flow. - Like other sympathetic ganglia, it releases norepinephrine at target organ synapses, but it does not serve as a major endocrine gland for systemic catecholamine release.