NEET-PG 2013 Practice Questions

Q: Follicles are present in which part of lymph nodes?

Cortex. ***Cortex*** - The **cortex** of a lymph node contains lymphoid follicles, which are sites of **B cell proliferation** and differentiation. - These follicles can be primary (inactive) or secondary (active, with a **germinal center**) based on ongoing immune responses. *Red pulp* - The **red pulp** is a component of the **spleen**, not lymph nodes. - It is primarily involved in filtering blood, removing old or damaged red blood cells, and storing monocytes. *White pulp* - The **white pulp** is also a component of the **spleen**, organized around central arterioles. - It contains periarteriolar lymphoid sheaths (PALS) with T cells and lymphoid follicles with B cells. *Medulla* - The **medulla** of a lymph node is the central region, rich in **medullary cords** (containing plasma cells, macrophages, and B cells) and **medullary sinuses**. - While lymphocytes are present, the organized structures of follicles are characteristic of the cortex.

Q: Ether was first used as an anesthetic by?

Morton. ***Morton*** - **William T.G. Morton**, a dentist, publicly demonstrated the use of **ether as a surgical anesthetic** in 1846 during a tooth extraction at Massachusetts General Hospital. - This event marked a pivotal moment in medicine, revolutionizing surgical practices by providing effective pain relief. *Priestly* - **Joseph Priestley** was an 18th-century chemist who discovered several gases, including **oxygen**, but was not involved in the anesthetic use of ether. - His work was foundational to understanding the composition of air but did not extend to surgical applications of inhaled substances. *Wells* - **Horace Wells**, an American dentist, was an early pioneer in anesthesia who experimented with **nitrous oxide** as an anesthetic for tooth extractions. - While significant, his work predated and differed from Morton's successful public demonstration and widespread adoption of ether. *Simpson* - **James Young Simpson**, a Scottish obstetrician, is credited with pioneering the use of **chloroform** as an anesthetic, particularly in childbirth. - His contributions were later than Morton's use of ether and involved a different anesthetic agent.

Q: Which of the following amino acids is found in keratin?

All of the options. ***All of the options*** - **Keratin** is a fibrous structural protein that forms the main component of hair, skin, and nails - All three amino acids listed - **Histidine, Lysine, and Arginine** - are indeed found in keratin's composition - **Lysine** and **Arginine** are basic amino acids that contribute to keratin's structural stability and are involved in ionic interactions - **Histidine** is also present and plays a role in the protein's functional and structural aspects - While keratin is particularly rich in **cysteine** (which forms disulfide bonds responsible for its strength), it also contains significant amounts of these other amino acids - The complete amino acid composition of keratin includes all of these and many other amino acids working together to provide its characteristic properties *Why individual options alone are incomplete* - Selecting only **Histidine**, **Lysine**, or **Arginine** individually would be incorrect because it would imply the other amino acids are NOT found in keratin - Since the question asks which amino acid "is found" in keratin and all three ARE present, the correct answer must acknowledge all of them

Q: Which form of tetrahydrofolate (THF) serves as the central intermediate in the one-carbon pool and is most directly involved in thymidine synthesis?

Methylene THF. ***Methylene THF*** - **N5,N10-Methylene tetrahydrofolate** is the direct **one-carbon donor** for the methylation of deoxyuridylate (dUMP) to deoxythymidylate (dTMP) by the enzyme **thymidylate synthase**, which is crucial for **DNA synthesis**. - During this reaction, **methylene THF** is oxidized to **dihydrofolate (DHF)**, requiring reduction by **dihydrofolate reductase** (DHFR) to regenerate THF. *Methyl THF* - **N5-Methyl tetrahydrofolate** is primarily involved in the **methionine synthase** reaction to convert **homocysteine to methionine**, requiring **vitamin B12**. - It is not directly involved in thymidine synthesis but plays a role in remethylation pathways and the **folate trap** when B12 is deficient. *None of the options* - This option is incorrect because **methylene THF** is indeed a direct participant in thymidine synthesis, serving as the critical one-carbon donor. - The roles of various THF forms in one-carbon metabolism are well-defined, and one of them is specifically responsible for this function. *Formyl THF* - **N10-Formyl tetrahydrofolate** is essential for the synthesis of **purine nucleotides** by donating formyl groups at two steps in the purine ring formation. - While important for nucleic acid synthesis, it does not directly contribute the methyl group needed for thymidine synthesis from dUMP.

Q: Which of the following is NOT a recommended primary management option for a patient with a snake bite?

Wash with soap and water. ***Wash with soap and water*** - Washing the bite with soap and water is **NOT** a recommended primary management option for a snake bite as it can spread the **venom**, potentially worsening the local effects and systemic absorption [1]. - The focus should be on **immobilization and minimizing movement** to restrict venom spread [1], [3]. *Splinting and immobilization* - **Immobilization** of the bitten limb is crucial to reduce venom dissemination through the **lymphatic system** [1], [2]. - This helps to **slow the absorption** of venom into the systemic circulation [1], [3]. *Reassure the patient* - **Anxiety and panic** can increase heart rate and metabolism, potentially accelerating venom absorption. - **Reassurance** helps to calm the patient, which can slow the spread of venom and improve cooperation with treatment [1], [2]. *Keep the site of bite below heart level* - Keeping the affected limb **below heart level** helps to reduce blood flow and, consequently, the systemic spread of venom [1]. - This simple maneuver can **delay the onset** of systemic toxic effects [1].

Q: Tinea cruris is caused by which of the following fungi?

Epidermophyton. ***Epidermophyton*** - **_Epidermophyton floccosum_** is one of the common dermatophytes responsible for causing **tinea cruris** (jock itch) and tinea pedis (athlete's foot). - **Note:** Tinea cruris can be caused by multiple dermatophytes including **_Trichophyton rubrum_** (most common), **_T. mentagrophytes_**, and **_E. floccosum_**. Among the options listed, Epidermophyton is the only dermatophyte that commonly causes tinea cruris. - Microscopic examination of skin scrapings shows **septate hyphae**, and it typically invades the stratum corneum but **not hair or nails**. *Trichosporon* - **_Trichosporon_** species cause **white piedra** (a fungal infection of the hair shaft) and can cause systemic infections in immunocompromised individuals. - It is **not a dermatophyte** and does not cause tinea cruris. *Microsporum* - **_Microsporum_** species are primarily associated with **tinea capitis** (ringworm of the scalp) and **tinea corporis** (ringworm of the body). - While Microsporum can occasionally involve skin in the groin region, it is **rarely implicated in classic tinea cruris** and is not considered a typical causative agent compared to Trichophyton or Epidermophyton species. *Candida* - **_Candida_** species (e.g., **_Candida albicans_**) cause candidiasis, which commonly presents as **intertrigo** in skin folds, oral thrush, or vaginal yeast infections. - While it can occur in the groin area (**candidal intertrigo**), it is **not a dermatophyte** and is distinctly different from tinea cruris, often presenting with **satellite lesions** and an intensely erythematous, macerated rash.

Q: What is the predominant bacterial genus found in the human colon?

Bacteroides. ***Bacteroides*** - **Bacteroides** is the most abundant bacterial genus in the human colon, representing a significant proportion of the gut microbiota. - The colon is a predominantly **anaerobic environment**, which is ideal for Bacteroides growth. - This genus belongs to the phylum Bacteroidetes and plays crucial roles in **polysaccharide fermentation** and vitamin synthesis. *Escherichia* - While **Escherichia coli** is well-known and commonly studied, it represents only a small fraction (typically <1%) of the total colonic bacteria. - E. coli is a facultative anaerobe but is vastly outnumbered by obligate anaerobes like Bacteroides. *Clostridium* - **Clostridium** is an important genus within the phylum Firmicutes and is abundant in the colon. - However, as a single genus, it does not reach the numerical dominance of Bacteroides. - Multiple Clostridium species contribute to butyrate production and gut health. *Staphylococcus* - **Staphylococcus** species are typically found in higher concentrations on the skin and in nasal passages. - In the colon, they are present in very small numbers and are not among the predominant genera.

Q: Lysis of a bacterial colony in a culture is caused by which agent?

Bacteriophage. ***Bacteriophage*** - **Bacteriophages** are viruses that infect and **lyse bacteria**, creating clear zones (plaques) on a bacterial lawn. - The lysis of bacterial colonies by bacteriophages is a fundamental observation in **microbiology** used to detect and quantify these viruses. *Pox* - **Poxviruses** infect animal cells, not bacteria, and cause diseases like smallpox or cowpox. - Their replication cycle involves host cell machinery but does not result in the *lysis* of bacterial colonies. *HSV* - **Herpes Simplex Virus (HSV)** is a human virus that causes oral and genital lesions. - HSV infects human cells and does not target or lyse bacterial colonies in culture. *CMV* - **Cytomegalovirus (CMV)** is another human virus, part of the herpesvirus family, causing a wide range of clinical manifestations. - CMV infection is specific to human cells and does not cause lysis of bacterial colonies.

Q: Dysfunctional uterine bleeding (DUB) is best treated by:

Progestogen. ***Progestogen*** - **Progestogen** therapy helps stabilize the **endometrium**, reducing excessive or irregular bleeding in DUB by counteracting unopposed estrogen. - It induces a more organized shedding of the uterine lining, which can regularize the menstrual cycle. *Curettage of uterus* - While **curettage** can provide temporary relief by removing the endometrial lining, it is primarily a diagnostic procedure to rule out pathology rather than a primary long-term treatment for DUB. - It does not address the underlying hormonal imbalance that causes DUB, leading to a high recurrence rate of symptoms. *Estrogen* - **Estrogen** therapy alone is generally not used to treat DUB because unopposed estrogen is often the cause of DUB, leading to **endometrial overgrowth** and irregular shedding. - Administering estrogen without a progestin could exacerbate the condition and increase endometrial proliferation. *Clomiphene* - **Clomiphene** is an anti-estrogen medication primarily used to induce **ovulation** in women with infertility. - It is not indicated for the management of dysfunctional uterine bleeding or for regulating menstrual cycles directly.

Q: What is the chance of a child having cystic fibrosis if both parents are carriers of the disease?

25%. ***50%*** - If one parent is affected by cystic fibrosis (CF), they are **homozygous for the CFTR mutation**, while the normal parent is likely **homozygous for the normal allele**. - Each child has a **50% chance** of inheriting the **mutated allele** from the affected parent, resulting in an **autosomal recessive** inheritance pattern [1]. *70%* - This percentage does not reflect the inheritance probabilities associated with **autosomal recessive traits** [1], such as cystic fibrosis. - In heterozygous and normal arrangements, the calculation does not support a **70%** inheritance chance of the disease. *80%* - Similarly, an **80% chance** is inaccurate as cystic fibrosis requires two mutated alleles for the disease to manifest [1]. - The inheritance pattern does not allow for a higher than **50% chance** when one parent is normal. *25%* - A **25% chance** applies if both parents were carriers of the CFTR mutation [1]. However, with only one affected parent, this percentage does not apply. - The maximum **chance of inheritance** from one affected and one normal parent is accurately stated as **50%**. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 53-54.

Question 1

Follicles are present in which part of lymph nodes?

Accepted Answer

Cortex

Answer

Red pulp

Answer

White pulp

Answer

Medulla

Question 2

Ether was first used as an anesthetic by?

Accepted Answer

Morton

Answer

Wells

Answer

Simpson

Answer

Priestly

Question 3

Which of the following amino acids is found in keratin?

Accepted Answer

All of the options

Answer

Lysine

Answer

Histidine

Answer

Arginine

Question 4

Which form of tetrahydrofolate (THF) serves as the central intermediate in the one-carbon pool and is most directly involved in thymidine synthesis?

Accepted Answer

Methylene THF

Answer

None of the options

Answer

Methyl THF

Answer

Formyl THF

Question 5

Which of the following is NOT a recommended primary management option for a patient with a snake bite?

Accepted Answer

Wash with soap and water

Answer

Reassure the patient

Answer

Splinting and immobilization

Answer

Keep the site of bite below heart level

Question 6

Tinea cruris is caused by which of the following fungi?

Accepted Answer

Epidermophyton

Answer

Trichosporon

Answer

Microsporum

Answer

Candida

Question 7

What is the predominant bacterial genus found in the human colon?

Accepted Answer

Bacteroides

Answer

Escherichia

Answer

Clostridium

Answer

Staphylococcus

Question 8

Lysis of a bacterial colony in a culture is caused by which agent?

Accepted Answer

Bacteriophage

Answer

Pox

Answer

HSV

Answer

CMV

Question 9

Dysfunctional uterine bleeding (DUB) is best treated by:

Accepted Answer

Progestogen

Answer

Curettage of uterus

Answer

Estrogen

Answer

Clomiphene

Question 10

What is the chance of a child having cystic fibrosis if both parents are carriers of the disease?

Accepted Answer

25%

Answer

75%

Answer

50%

Answer

0%

Answer

100%

NEET-PG 2013

Anatomy

Anesthesiology

Biochemistry

Forensic Medicine

Microbiology

Obstetrics and Gynecology

Psychiatry