NEET-PG 2025 Practice Questions

Q: 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?

GM2 ganglioside. ***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.

Q: 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?

Partial protein production. ***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.

Q: 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?

Nucleotide excision repair. ***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.

Q: 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?

Thiamine. 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.

Q: 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?

Type IIa. ***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.

Q: 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?

Enterobius vermicularis. ***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.

Q: Most common cause of squamous cell carcinoma at the base of the tongue is:

HPV. ***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.

Q: 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?

Fibrillin-1 (FBN1). ***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.

Q: Which of the following types of cell death involves activation of caspase enzymes?

Apoptosis and Pyroptosis. ***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 1

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?

Accepted Answer

GM2 ganglioside

Answer

GM1 ganglioside

Answer

Sphingomyelin

Answer

Glucocerebroside

Question 2

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?

Accepted Answer

Partial protein production

Answer

Complete change in protein production

Answer

No protein production

Answer

No change in the final protein

Question 3

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?

Accepted Answer

Nucleotide excision repair

Answer

Base excision repair

Answer

Mismatch repair

Answer

Non-homologous end joining (NHEJ)

Question 4

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?

Accepted Answer

Thiamine

Answer

Vitamin B12

Answer

Zinc

Answer

Selenium

Question 5

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?

Accepted Answer

Type IIa

Answer

Type I

Answer

Type II

Answer

Type IIb

Question 6

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?

Accepted Answer

Enterobius vermicularis

Answer

Hymenolepis nana

Answer

Trichuris trichiura

Answer

Ancylostoma duodenale

Question 7

Most common cause of squamous cell carcinoma at the base of the tongue is:

Accepted Answer

HPV

Answer

EBV

Answer

HCV

Answer

CMV

Question 8

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?

Accepted Answer

Fibrillin-1 (FBN1)

Answer

COL4A5

Answer

Elastin

Answer

COL1A1

Question 9

Which of the following types of cell death involves activation of caspase enzymes?

Accepted Answer

Apoptosis and Pyroptosis

Answer

Necrosis and Apoptosis

Answer

Apoptosis only

Answer

Apoptosis and necroptosis

Question 10

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?

Accepted Answer

t(15 ; 17)

Answer

t(14 ; 18)

Answer

inv(16)

Answer

t(8 ; 21)

NEET-PG 2025

Biochemistry

Internal Medicine

Microbiology

Pathology