Biochemistry
3 questionsA neonate presents with seizures and is found to have a cherry red spot on fundus examination. Enzyme assay reveals deficiency of hexosaminidase A. Which of the following substances is most likely to be accumulated in this patient?
A frameshift mutation occurs due to the insertion of a new nucleotide at the 4th position of an mRNA sequence with 900 nucleotides. What is the most likely outcome of this mutation?
A patient presents with skin cancer and hyperpigmentation that worsens with sunlight exposure. Which of the following DNA repair mechanisms is most likely defective in this condition?
NEET-PG 2025 - Biochemistry NEET-PG Practice Questions and MCQs
Question 41: A neonate presents with seizures and is found to have a cherry red spot on fundus examination. Enzyme assay reveals deficiency of hexosaminidase A. Which of the following substances is most likely to be accumulated in this patient?
- A. GM1 ganglioside
- B. Sphingomyelin
- C. GM2 ganglioside (Correct Answer)
- D. Glucocerebroside
Explanation: ***GM2 ganglioside*** - Deficiency of **Hexosaminidase A** results in the accumulation of **GM2 ganglioside**, defining features of **Tay-Sachs disease**. - The accumulation of GM2 ganglioside in the retina's ganglion cells causes the characteristic **cherry red spot** on fundus examination. *GM1 ganglioside* - The accumulation of **GM1 ganglioside** occurs in **GM1 gangliosidosis**, due to a deficiency of **β-galactosidase**. - GM1 gangliosidosis typically presents with coarse facial features, hepatosplenomegaly, and skeletal deformities (**dysostosis multiplex**), features not always prominent in Tay-Sachs. *Sphingomyelin* - Accumulation of **Sphingomyelin** is the diagnostic feature of **Niemann-Pick disease** (especially Type A), caused by a deficiency of **sphingomyelinase**. - While Niemann-Pick Type A also causes a cherry red spot, it is classically associated with rapid neurodegeneration and marked **hepatosplenomegaly** and **foam cells** (lipid-laden macrophages). *Glucocerebroside* - This lipid accumulates in **Gaucher disease** because of deficient **glucocerebrosidase** activity. - Gaucher disease is characterized by bony involvement, pancytopenia, and massive **hepatosplenomegaly**, and does not typically feature the cherry red spot.
Question 42: A frameshift mutation occurs due to the insertion of a new nucleotide at the 4th position of an mRNA sequence with 900 nucleotides. What is the most likely outcome of this mutation?
- A. Partial protein production (Correct Answer)
- B. Complete change in protein production
- C. No protein production
- D. No change in the final protein
Explanation: ***Partial protein production*** - The insertion of a single nucleotide at position 4 causes a **frameshift mutation**, which fundamentally alters the reading frame starting from the second codon. - Frameshift mutations typically lead to the introduction of a **Premature Termination Codon (PTC)** shortly downstream, resulting in the synthesis of a **truncated** (partial) and non-functional protein. *No change in the final protein* - A change from position 4 onward affects almost the entire coding sequence; thus, there cannot be **no change** in the protein structure. - Only an insertion/deletion of a multiple of three nucleotides (in-frame mutation) or a mutation late in the sequence might result in a preserved protein function. *Complete change in protein production* - While the subsequent mRNA sequence is entirely changed, the outcome on the protein level is usually **truncation** (partial protein), not the complete synthesis of a full-length, completely altered protein. - The term "complete change" is less accurate than "partial production," as the protein synthesis is typically **aborted prematurely**. *No protein production* - The **start codon** (positions 1-3) is upstream of the mutation site (position 4) and remains intact, allowing for **translation initiation** to occur normally. - Protein production starts; it is only terminated prematurely when a stop codon is encountered in the shifted reading frame.
Question 43: A patient presents with skin cancer and hyperpigmentation that worsens with sunlight exposure. Which of the following DNA repair mechanisms is most likely defective in this condition?
- A. Base excision repair
- B. Mismatch repair
- C. Nucleotide excision repair (Correct Answer)
- D. Non-homologous end joining (NHEJ)
Explanation: ***Nucleotide excision repair*** - This mechanism is responsible for repairing large, bulky DNA lesions, most notably **pyrimidine dimers** caused by **UV radiation** (sunlight). - A defect in NER is the underlying cause of **Xeroderma Pigmentosum**, which presents with severe photosensitivity, hyperpigmentation, and a significantly increased risk of **skin cancer** (melanoma and non-melanoma). *Base excision repair* - Primarily repairs **small, non-helix-distorting lesions** caused by spontaneous factors (like deamination) or oxidative damage, such as single base modifications. - Defective BER is implicated in hereditary cancers like MUTYH-associated polyposis (MAP), which is not associated with **UV-induced skin pathology**. *Non-homologous end joining (NHEJ)* - Responsible for repairing **double-strand breaks (DSBs)** in DNA, usually in the G0/G1 phase of the cell cycle. - While critical for genome stability, defects in NHEJ lead to severe immunodeficiency (due to impaired V(D)J recombination) and are not the primary cause of susceptibility to **solar-induced skin cancer**. *Mismatch repair* - Corrects errors (mismatched bases) incorporated during **DNA replication** that escape proofreading. - Defective MMR leads to a high frequency of microsatellite instability, characteristic of conditions like **Hereditary Non-polyposis Colorectal Cancer (HNPCC)** or Lynch syndrome, but not the primary cause of photosensitivity and UV-related skin cancer.
Internal Medicine
2 questionsA patient on long-term hydrochlorothiazide therapy presents with features of neuropathy, heart failure, and symmetrical tingling sensations. Which of the following nutrient deficiencies is most likely responsible?
A patient presents with elevated total cholesterol, subcutaneous xanthomas, and a positive family history of similar findings. Triglyceride levels are normal (<140 mg/dL). What is the most likely type of familial dyslipidemia?
NEET-PG 2025 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 41: A patient on long-term hydrochlorothiazide therapy presents with features of neuropathy, heart failure, and symmetrical tingling sensations. Which of the following nutrient deficiencies is most likely responsible?
- A. Thiamine (Correct Answer)
- B. Vitamin B12
- C. Zinc
- D. Selenium
Explanation: Thiamine - The combination of **neuropathy** (symmetrical tingling sensations) and **heart failure** (cardiomyopathy) is the classic manifestation of **Beriberi**, caused by Thiamine (Vitamin B1) deficiency [1]. - **Wet Beriberi** causes high-output **cardiac failure**, while **Dry Beriberi** is responsible for **symmetrical peripheral neuropathy** [1]. *Selenium* - Selenium deficiency causes **Keshan disease**, which is characterized by **cardiomyopathy**, but the simultaneous presentation of specific symmetrical peripheral neuropathy is less common. - Deficiency can also lead to muscle pain and weakness, but often does not perfectly match this triad. *Vitamin B12* - Deficiency causes **Subacute Combined Degeneration** (neuropathy and myelopathy) and **megaloblastic anemia**, but severe acute heart failure is not a defining feature. - Neuropathy typically involves a mix of sensory, motor, and central nervous system signs, but the heart failure component is missing. *Zinc* - Zinc deficiency primarily causes **acrodermatitis enteropathica** (dermatitis), impaired wound healing, and immune dysfunction. - It is not a common cause of either **heart failure** or widespread peripheral neuropathy.
Question 42: A patient presents with elevated total cholesterol, subcutaneous xanthomas, and a positive family history of similar findings. Triglyceride levels are normal (<140 mg/dL). What is the most likely type of familial dyslipidemia?
- A. Type I
- B. Type IIa (Correct Answer)
- C. Type II
- D. Type IIb
Explanation: ***Type IIa*** - This type, also known as **Familial Hypercholesterolemia**, is characterized by severely elevated **Total (LDL) Cholesterol** and **normal triglyceride** levels (<140 mg/dL) [1]. - The presence of **subcutaneous xanthomas** (often reflecting tendon xanthomas) and a strong family history are classic findings associated with defective **LDL receptors** [1]. *Type I* - This type (Familial Hyperchylomicronemia) is characterized by extremely high **Triglyceride** levels and chylomicrons due to **Lipoprotein Lipase (LPL) deficiency** or C-II deficiency. - The key clinical feature is usually recurrent **pancreatitis** and **eruptive xanthomas**, contrary to the normal TGs seen in this patient. *Type IIb* - This type is defined by elevated levels of both **Total/LDL Cholesterol** and **Triglycerides** (as VLDL) [1]. - An elevated triglyceride level would be mandatory for a Type IIb classification, differentiating it from the patient's normal triglyceride levels. *Type II* - Type II is the broad classification covering all dyslipidemias with elevated **LDL cholesterol** (both IIa and IIb). - For a precise diagnosis in the Fredrickson system, the specific subtype (**IIa** based on normal TGs) is required.
Microbiology
1 questionsA 5-year-old child presents with nocturnal perianal itching. The image below shows the organism identified on an adhesive tape test. What is the most likely causative agent?
NEET-PG 2025 - Microbiology NEET-PG Practice Questions and MCQs
Question 41: A 5-year-old child presents with nocturnal perianal itching. The image below shows the organism identified on an adhesive tape test. What is the most likely causative agent?
- A. Hymenolepis nana
- B. Trichuris trichiura
- C. Enterobius vermicularis (Correct Answer)
- D. Ancylostoma duodenale
Explanation: ***Enterobius vermicularis*** - The clinical presentation of **nocturnal perianal itching** (pruritus ani) in a child is highly characteristic of **pinworm infection** (enterobiasis). - The image shows a classic **D-shaped** or planoconvex egg, frequently found on the **adhesive tape test**, which are key identifiers for *Enterobius vermicularis*. *Ancylostoma duodenale* - This parasite causes **hookworm disease**, typically manifesting as **iron-deficiency anemia** and rarely perianal itching. - *Ancylostoma* eggs are oval, thin-shelled, and typically found in the **stool**, not via a tape test. *Hymenolepis nana* - This is the **dwarf tapeworm**, which usually causes mild or asymptomatic infection, though heavy infections can cause abdominal discomfort. - The eggs are small, oval, and possess **polar filaments** between the shell and the oncosphere, which are absent in the image. *Trichuris trichiura* - This parasite, the **whipworm**, causes trichuriasis, which presents with bloody diarrhea and occasionally **rectal prolapse** in heavy infections. - *Trichuris* eggs are distinctively **barrel-shaped** with two prominent bipolar mucoid plugs at each end.
Pathology
4 questionsMost common cause of squamous cell carcinoma at the base of the tongue is:
A 22-year-old tall male presents with long limbs, increased arm span, hypermobile joints, and high-arched palate. On examination, he has lens subluxation and a diastolic murmur suggestive of aortic root dilation. Which of the following genes is most likely mutated in this condition?
Which of the following types of cell death involves activation of caspase enzymes?
A 68-year-old man presents with bleeding manifestations. Peripheral smear shows the presence of cells shown below. Which of the following is the most common chromosomal abnormality seen in this condition?
NEET-PG 2025 - Pathology NEET-PG Practice Questions and MCQs
Question 41: Most common cause of squamous cell carcinoma at the base of the tongue is:
- A. EBV
- B. HCV
- C. HPV (Correct Answer)
- D. CMV
Explanation: ***HPV*** - **Human Papillomavirus**, particularly **HPV-16**, is the predominant etiological factor for **squamous cell carcinoma (SCC) of the oropharynx**, which includes the base of the tongue [1]. - **HPV-positive SCC** has rapidly increased in incidence and constitutes the majority of these cancers in non-smokers and non-drinkers [1]. *EBV* - **Epstein-Barr Virus (EBV)** is strongly associated with **Nasopharyngeal Carcinoma (NPC)**, endemic Burkitt's lymphoma, and post-transplant lymphoproliferative disorder [2]. - It is not considered the primary or most common oncogenic agent for **base of tongue SCC** [2]. *HCV* - **Hepatitis C Virus (HCV)** is the chief cause of viral **Hepatocellular Carcinoma (HCC)** and is also linked to certain **B-cell non-Hodgkin's lymphomas**. - There is no established role for HCV in the pathogenesis or high prevalence of **squamous cell carcinoma of the head and neck**. *CMV* - **Cytomegalovirus (CMV)** is a herpesvirus typically associated with opportunistic infections (e.g., retinitis, colitis) in **immunocompromised patients**. - While studies have investigated its oncogenic potential, CMV is not a significant or common causative agent for **oral or pharyngeal SCC**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 738-741. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Head and Neck, pp. 744-745.
Question 42: A 22-year-old tall male presents with long limbs, increased arm span, hypermobile joints, and high-arched palate. On examination, he has lens subluxation and a diastolic murmur suggestive of aortic root dilation. Which of the following genes is most likely mutated in this condition?
- A. Fibrillin-1 (FBN1) (Correct Answer)
- B. COL4A5
- C. Elastin
- D. COL1A1
Explanation: ***Fibrillin-1 (FBN1)*** - The clinical presentation (tall stature, long limbs, increased arm span, aortic root dilation, and lens subluxation/ectopia lentis) is characteristic of **Marfan Syndrome** [1]. - Marfan syndrome is caused by an autosomal dominant mutation in the **FBN1 gene** on chromosome 15, which codes for the microfibrillar protein **fibrillin-1** [1]. *COL4A5* - Mutations in **COL4A5** (Type IV collagen) are associated with **Alport Syndrome**. - Alport syndrome primarily presents with **progressive sensorineural hearing loss**, ocular abnormalities (not typically lens subluxation), and **nephropathy** (hematuria/proteinuria). *COL1A1* - Mutations in **COL1A1** (Type I collagen) are most commonly associated with **Osteogenesis Imperfecta (OI)**. - OI is characterized by **recurrent fractures**, often with blue sclerae, hearing loss, and joint laxity, but not the specific cardiovascular and ocular features seen here. *Elastin* - Mutations in the **Elastin gene (ELN)** are responsible for **Supravalvular Aortic Stenosis (SVAS)**, often seen in **Williams Syndrome**. - Williams syndrome also involves intellectual disability and a characteristic 'elfin' facies, which are not mentioned in this patient's presentation. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 153-154.
Question 43: Which of the following types of cell death involves activation of caspase enzymes?
- A. Necrosis and Apoptosis
- B. Apoptosis and Pyroptosis (Correct Answer)
- C. Apoptosis only
- D. Apoptosis and necroptosis
Explanation: ***Apoptosis and Pyroptosis*** - **Apoptosis** is the classic caspase-dependent programmed cell death pathway [1] - Involves **initiator caspases** (Caspase-8, Caspase-9) and **executioner caspases** (Caspase-3, -6, -7) - Characterized by cell shrinkage, chromatin condensation, and apoptotic body formation - **Pyroptosis** is an inflammatory form of programmed cell death that is strictly caspase-dependent [2] - Mediated by **inflammatory caspases** (Caspase-1, -4, -5, -11) [2] - Involves cleavage of Gasdermin-D leading to membrane pore formation - Triggered by inflammasome activation (particularly NLRP3) *Necrosis and Apoptosis* - **Necrosis** is caspase-independent and represents unregulated cell death from acute injury - Characterized by cell swelling, membrane rupture, and inflammatory response - Does not involve programmed activation of caspase enzymes *Apoptosis and necroptosis* - **Necroptosis** is a regulated form of necrotic cell death that occurs in a **caspase-independent** manner [2] - Executed through RIPK1-RIPK3-MLKL kinase pathway [2] - Typically occurs when caspase activity is inhibited or blocked *Apoptosis only* - Incomplete answer as **pyroptosis** is also inherently caspase-dependent - Pyroptosis uses inflammatory caspases (Caspase-1/4/5) distinct from apoptotic caspases - Both pathways represent distinct forms of caspase-mediated programmed cell death **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 64-67. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, p. 71.
Question 44: A 68-year-old man presents with bleeding manifestations. Peripheral smear shows the presence of cells shown below. Which of the following is the most common chromosomal abnormality seen in this condition?
- A. t(15 ; 17) (Correct Answer)
- B. t(14 ; 18)
- C. inv(16)
- D. t(8 ; 21)
Explanation: The image displays a large blast cell containing numerous needle-like pink/red inclusions known as **Auer rods** (sometimes referred to as a "faggot cell") [2]. This morphology is pathognomonic for **Acute Promyelocytic Leukemia (APL)**, which is categorized as **AML M3** [3]. APL is frequently associated with severe **Disseminated Intravascular Coagulation (DIC)**, explaining the patient's bleeding manifestations [3]. ***t(15 ; 17)*** - This specific reciprocal translocation fuses the **PML** (Promyelocytic Leukemia) gene on chromosome 15 with the **RARA** (Retinoic Acid Receptor Alpha) gene on chromosome 17, defining APL [1]. - The resulting **PML-RARA fusion protein** blocks myeloid differentiation, and its presence guides therapeutic management, making APL highly responsive to **All-trans Retinoic Acid (ATRA)** [1]. *t(8 ; 21)* - This translocation is the most common cytogenetic abnormality seen in **AML M2** (AML with maturation), fusing the *RUNX1* and *RUNX1T1* genes [3]. - Although classified as core-binding factor leukemia, it lacks the characteristic morphology (multiple Auer rods/faggot cells) of APL. *t(14 ; 18)* - This is the defining translocation for **Follicular Lymphoma**, leading to the overexpression of the anti-apoptotic protein **BCL2**. - It is not associated with Acute Myeloid Leukemia (AML) subtypes. *inv(16)* - This chromosomal inversion is highly characteristic of **AML M4eo** (Acute Myelomonocytic Leukemia with marrow eosinophilia) [3]. - This aberration fuses the *CBFB* gene with *MYH11*, another type of core-binding factor leukemia with a largely favorable prognosis [3]. **References:** [1] 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. 620-621. [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. 621-622. [3] 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, p. 620.