NEET-PG 2012 Practice Questions

Q: Corpora arenacea is seen in?

Pineal. ***Pineal*** - **Corpora arenacea**, also known as **brain sand**, are calcium deposits found in the pineal gland. - Their presence is a normal, age-related finding and increases with age, though their exact physiological role is not fully understood. *Prostate* - The prostate gland contains **corpora amylacea**, which are concentric calcifications found within the glandular acini. - While similar in appearance to corpora arenacea, they are distinct structures specific to the prostate. *Seminal vesicle* - The seminal vesicles produce a fluid component of semen, and while they may occasionally show calcifications, these are typically due to stones or chronic inflammation, not the characteristic "brain sand" seen in the pineal gland. - They do not contain corpora arenacea as a normal physiological feature. *Breast* - Calcifications in the breast are common and can be either benign (e.g., **fibrocystic changes**, vascular calcifications) or malignant (e.g., **ductal carcinoma in situ**). - These calcifications are generally not referred to as corpora arenacea and have different clinical implications and microscopic appearances.

Q: Primary and secondary palates are divided by

Incisive foramen. ***Incisive foramen*** - The **incisive foramen** is an anatomical landmark located just posterior to the central incisors, and it marks the boundary between the developmentally distinct primary and secondary palates. - The **primary palate** develops from the median palatine process, while the **secondary palate** develops from the palatal shelves of the maxillary prominences [1]. *Greater palatine foramen* - The **greater palatine foramen** is located near the posterior border of the hard palate, transmitting the greater palatine nerve and vessels. - It lies within the **secondary palate** and does not delineate the boundary between the primary and secondary palatal structures. *Canine teeth* - The **canine teeth** are part of the dental arch and play a role in mastication. - While located in the anterior part of the oral cavity, they are not a developmental or anatomical boundary marker for palatal divisions [1]. *Alveolar arch* - The **alveolar arch** is the bone that supports the teeth, forming the curved ridge of the maxilla and mandible [1]. - It is distinct from the palate and does not serve as a divider between the primary and secondary palatal components.

Q: Which of the following cell types is neuroectodermal in origin?

Smooth muscle cells. ***Smooth muscle cells*** - This is the **correct answer** based on a **specific exception**: smooth muscle cells of the **iris dilator and sphincter muscles** and the **ciliary muscle** in the eye are derived from **neuroectoderm** (specifically from the **optic cup**, an outgrowth of the neural tube). - **Important note:** The vast majority of smooth muscle in the body is of **mesodermal origin** (e.g., in blood vessels, GI tract, respiratory tract). This question tests knowledge of this **notable embryological exception**. - In the context of the given options, this is the only cell type with any neuroectodermal component. *Skeletal muscle cells* - Skeletal muscle cells are entirely derived from the **paraxial mesoderm**, specifically from **somites** (myotome portion). - They form the voluntary muscles of the body and are **never** of neuroectodermal origin. *Endothelial cells* - Endothelial cells lining blood vessels and lymphatic vessels are derived from the **mesoderm** (specifically from **angioblasts**). - They are part of the cardiovascular system and are **entirely mesodermal** in origin. *Cardiac muscle cells* - Cardiac muscle cells are derived from the **splanchnic mesoderm** (lateral plate mesoderm). - The heart musculature is **entirely mesodermal** with no neuroectodermal contribution. **Clinical Pearl:** Classic neuroectodermal derivatives include neurons, glial cells (astrocytes, oligodendrocytes), ependymal cells, and neural crest derivatives (Schwann cells, melanocytes, chromaffin cells). The smooth muscle of the iris represents an important exception to the general rule that smooth muscle is mesodermal.

Q: Which of the following substances is not derived from tyrosine?

Nicotinic acid. ***Nicotinic acid*** - **Nicotinic acid** (niacin, vitamin B3) is synthesized from **tryptophan** in the body, not tyrosine. - It plays a crucial role in metabolism as a precursor for NAD+ and NADH, which are involved in various enzymatic reactions. *Thyroxine* - **Thyroxine** (T4), a thyroid hormone, is derived from the amino acid **tyrosine**. - **Iodine** is incorporated into tyrosine residues on thyroglobulin to form monoiodotyrosine (MIT) and diiodotyrosine (DIT), which then couple to form T4 (and T3). *Melanin* - **Melanin**, the pigment responsible for skin, hair, and eye color, is synthesized from **tyrosine** through a pathway involving the enzyme **tyrosinase**. - This process involves the hydroxylation of tyrosine to 3,4-dihydroxyphenylalanine (DOPA) and subsequent oxidation reactions. *Dopamine* - **Dopamine**, an important neurotransmitter, is synthesized from **tyrosine** in a two-step process in the brain and adrenal medulla. - Tyrosine is first hydroxylated to DOPA by **tyrosine hydroxylase**, and then DOPA is decarboxylated to dopamine by DOPA decarboxylase.

Q: Pantothenic acid is needed for donating the following moiety?

Acetyl group. ***Acetyl group*** - **Pantothenic acid** (vitamin B5) is a crucial component of **coenzyme A (CoA)**, which plays a central role in transferring **acetyl groups**. - This transfer is vital in numerous metabolic pathways, including the **Krebs cycle**, fatty acid synthesis, and fatty acid oxidation. *Carboxyl* - The transfer of **carboxyl groups** is typically mediated by a different coenzyme, **biotin** (vitamin B7), not pantothenic acid. - Biotin-dependent enzymes are involved in carboxylation reactions like those in gluconeogenesis and fatty acid synthesis. *Hydroxyl* - While hydroxyl groups are common in organic chemistry, pantothenic acid's primary role is not the donation of isolated **hydroxyl groups**. - Hydroxyl groups are often donated or accepted during redox reactions or hydrolysis, often by specific enzymes directly. *Amino* - The transfer of **amino groups** is primarily associated with **pyridoxal phosphate (PLP)**, the active form of vitamin B6. - PLP-dependent enzymes, such as **transaminases**, are critical for amino acid metabolism.

Q: What is the primary function of reverse transcription?

Synthesis of DNA from an RNA template. ***Synthesis of DNA from an RNA template*** - **Reverse transcription** is catalyzed by the enzyme **reverse transcriptase**, which uses an **RNA template** to synthesize a complementary DNA (cDNA) strand. - This process is fundamental in the life cycle of **retroviruses** like HIV, allowing them to integrate their genetic material into the host genome. *Synthesis of RNA from a DNA template* - This process is known as **transcription**, where genetic information is copied from **DNA to RNA**, not the reverse. - It is a key step in gene expression, leading to the production of various types of RNA molecules. *Synthesis of DNA from a DNA template* - This describes **DNA replication**, the process by which DNA makes copies of itself, ensuring genetic continuity during cell division. - It involves enzymes like **DNA polymerase** and creates two identical DNA molecules from one original DNA molecule. *Synthesis of RNA from an RNA template* - This process is known as **RNA replication** and is characteristic of certain **RNA viruses** (e.g., influenza virus), where RNA serves as both the template and the genetic material. - It involves an enzyme called **RNA-dependent RNA polymerase**.

Q: The thickness of the endometrium at the time of implantation is:

7 - 10 mm. ***7 - 10 mm*** - At the time of **implantation** (day 6-10 post-fertilization, around day 20-24 of the menstrual cycle), the endometrium is in the **mid-secretory phase** and measures **7-10 mm** in thickness. - This is the **optimal thickness** for successful embryo implantation, characterized by a receptive endometrium with **decidualization**, **spiral artery development**, and **glycogen-rich glandular secretions**. - Endometrial thickness <7 mm is associated with **poor implantation rates** and reduced pregnancy success. *3 - 4 mm* - An endometrial thickness of 3-4 mm is **too thin** for successful implantation. - This thickness is typically seen in the **early proliferative phase** (immediately after menstruation), not during the implantation window. - Thin endometrium (<7 mm) is associated with **poor receptivity** and lower pregnancy rates in both natural conception and assisted reproduction. *20 - 30 mm* - An endometrial thickness of 20-30 mm is **abnormally thick** and not conducive to normal implantation. - Such thickness may indicate **endometrial hyperplasia**, **polyps**, or other pathological conditions requiring investigation. *30 - 40 mm* - An endometrial thickness of 30-40 mm is **severely abnormal** and would likely prevent successful implantation. - This extreme thickness suggests significant pathology such as **endometrial hyperplasia** or **malignancy** and requires urgent evaluation.

Q: Li–Fraumeni syndrome is associated with mutations in which of the following genes?

Gene TP53. ***Gene TP53*** - Li-Fraumeni syndrome is a rare, inherited cancer susceptibility syndrome associated with germline mutations in the **TP53 tumor suppressor gene**. - The **TP53 gene** encodes the p53 protein, which plays a critical role in cell cycle arrest, DNA repair, and initiation of apoptosis in response to cellular stress, thus preventing tumor formation. *Gene P21* - The **p21 gene** (CDKN1A) is a cyclin-dependent kinase inhibitor that acts downstream of p53, mediating p53-induced cell cycle arrest. - While p21 is involved in the p53 pathway, mutations in p21 itself are not the primary cause of Li-Fraumeni syndrome. *Gene RB1* - The **RB1 gene** encodes the retinoblastoma protein, a tumor suppressor involved in cell cycle regulation, particularly in controlling passage from G1 to S phase. - Mutations in **RB1** are primarily associated with hereditary retinoblastoma and osteosarcoma, not Li-Fraumeni syndrome. *Gene BRCA1* - The **BRCA1 gene** is a tumor suppressor gene involved in DNA repair, especially homologous recombination. - Germline mutations in **BRCA1** are strongly associated with hereditary breast and ovarian cancer syndrome, not Li-Fraumeni syndrome.

Q: Insensible water loss per day is ?

1000 ml. ***1000 ml*** - **Insensible water loss** occurs through the skin (evaporation) and respiratory tract (exhalation) without conscious perception. - The typical daily insensible water loss in an adult is approximately **800-1000 ml/day**. - **Breakdown**: Skin evaporation (~400-500 ml) + Respiratory tract (~300-400 ml) = **~900-1000 ml total**. - **1000 ml** is the standard value cited in major physiology textbooks (Guyton & Hall, Ganong) and is the most commonly accepted answer for NEET PG examinations. *100 ml* - This value is significantly **lower** than the actual insensible water loss, which occurs continuously throughout the day. - Such a low volume would imply negligible evaporation and respiratory loss, which is not physiologically accurate. *300 ml* - While greater than 100 ml, 300 ml is still **far below** the typical range for daily insensible water loss. - This amount represents only about one-third of the actual insensible losses from the skin and respiratory system combined. *700 ml* - Although this value is sometimes mentioned in literature, it is at the **lower end** of the physiological range. - The more widely accepted standard value for insensible water loss in a healthy adult under normal conditions is **900-1000 ml/day**. - 700 ml would underestimate the normal daily insensible losses.

Q: Ptyalin is secreted by?

Salivary gland. ***Salivary gland*** - **Ptyalin**, also known as **salivary amylase**, is an enzyme produced by the salivary glands. - Its primary role is to initiate the **digestion of carbohydrates** (starches) in the mouth. *Gastric gland* - Gastric glands primarily secrete **hydrochloric acid** and **pepsinogen**, involved in protein digestion. - They do not produce ptyalin or enzymes for carbohydrate digestion. *Duodenal gland* - Duodenal glands (Brunner's glands) secrete alkaline mucus to protect the duodenum from acidic chyme. - They are not involved in the production of carbohydrate-digesting enzymes like ptyalin. *Pancreatic gland* - The pancreas produces **pancreatic amylase**, which continues starch digestion in the small intestine. - While it secretes an amylase, it is distinct from salivary amylase (ptyalin) and released into the duodenum, not the mouth.

Question 1

Corpora arenacea is seen in?

Accepted Answer

Pineal

Answer

Seminal vesicle

Answer

Breast

Answer

Prostate

Question 2

Primary and secondary palates are divided by

Accepted Answer

Incisive foramen

Answer

Greater palatine foramen

Answer

Canine teeth

Answer

Alveolar arch

Question 3

Which of the following cell types is neuroectodermal in origin?

Accepted Answer

Smooth muscle cells

Answer

Skeletal muscle cells

Answer

Endothelial cells

Answer

Cardiac muscle cells

Question 4

Which of the following substances is not derived from tyrosine?

Accepted Answer

Nicotinic acid

Answer

Thyroxine

Answer

Melanin

Answer

Dopamine

Question 5

Pantothenic acid is needed for donating the following moiety?

Accepted Answer

Acetyl group

Answer

Carboxyl

Answer

Hydroxyl

Answer

Amino

Question 6

What is the primary function of reverse transcription?

Accepted Answer

Synthesis of DNA from an RNA template

Answer

Synthesis of RNA from a DNA template

Answer

Synthesis of DNA from a DNA template

Answer

Synthesis of RNA from an RNA template

Question 7

The thickness of the endometrium at the time of implantation is:

Accepted Answer

7 - 10 mm

Answer

20 - 30 mm

Answer

30 - 40 mm

Answer

3 - 4 mm

Question 8

Li–Fraumeni syndrome is associated with mutations in which of the following genes?

Accepted Answer

Gene TP53

Answer

Gene RB1

Answer

Gene BRCA1

Answer

Gene P21

Question 9

Insensible water loss per day is ?

Accepted Answer

1000 ml

Answer

100 ml

Answer

700 ml

Answer

300 ml

Question 10

Ptyalin is secreted by?

Accepted Answer

Salivary gland

Answer

Gastric gland

Answer

Duodenal gland

Answer

Pancreatic gland

NEET-PG 2012

Anatomy

Biochemistry

Obstetrics and Gynecology

Pathology

Physiology