Molecular Pathology Practice Questions

Q: Which syndrome is characterized by the occurrence of both colorectal and endometrial cancers?

Lynch syndrome. **Explanation:** **Lynch Syndrome (Hereditary Non-Polyposis Colorectal Cancer - HNPCC)** is the correct answer. It is an autosomal dominant condition caused by germline mutations in **DNA Mismatch Repair (MMR) genes** (MLH1, MSH2, MSH6, and PMS2), leading to microsatellite instability. While it carries the highest risk for colorectal cancer (CRC), the most common extra-colonic manifestation is **Endometrial Cancer**. In fact, for female patients with Lynch syndrome, the risk of endometrial cancer often equals or exceeds the risk of CRC. **Analysis of Incorrect Options:** * **Cowden Syndrome:** Part of the PTEN hamartoma tumor syndrome. It is characterized by multiple hamartomas, macrocephaly, and a high risk of **Breast, Thyroid (follicular), and Endometrial cancers**, but it is not primarily defined by the CRC-Endometrial duo. * **Turcot’s Syndrome:** A variant of polyposis syndromes (FAP or Lynch) characterized by the association of **Colorectal tumors and Central Nervous System (CNS) tumors** (Medulloblastoma in FAP; Glioblastoma in Lynch). * **Juvenile Polyposis Syndrome (JPS):** Characterized by multiple hamartomatous polyps in the GI tract. While it increases the risk of GI cancers, it is not typically associated with endometrial malignancy. **High-Yield Clinical Pearls for NEET-PG:** * **Amsterdam II Criteria (3-2-1 rule):** 3 relatives with Lynch-associated cancer, 2 successive generations, 1 diagnosed before age 50. * **Lynch-associated cancers:** Colorectal (right-sided predominance), Endometrial, Ovarian, Gastric, and Small Bowel. * **Screening:** For Lynch syndrome, colonoscopy is recommended every 1–2 years starting at age 20–25. Prophylactic hysterectomy and bilateral salpingo-oophorectomy (BSO) are often considered after childbearing is complete.

Q: What is the diagnosis suggested by the following karyotype?

Cri du chat syndrome. ***Cri du chat syndrome*** - The karyotype showing **deletion of the short arm of chromosome 5 (del 5p)** is diagnostic of Cri du chat syndrome. - Clinical features include **characteristic cat-like cry** in infants, **microcephaly**, **intellectual disability**, and **distinctive facial features**. *Down's syndrome* - Characterized by **trisomy 21** karyotype (47,XY,+21 or 47,XX,+21), not a deletion on chromosome 5. - Clinical features include **epicanthal folds**, **simian crease**, and **intellectual disability** with cardiac defects. *Turner's syndrome* - Shows **monosomy X** karyotype (45,X) or mosaic patterns, involving sex chromosomes not chromosome 5. - Clinical features include **short stature**, **webbed neck**, **shield chest**, and **ovarian dysgenesis**. *Patau Syndrome* - Demonstrates **trisomy 13** karyotype (47,XY,+13 or 47,XX,+13), not involving chromosome 5 deletion. - Clinical features include **holoprosencephaly**, **cleft lip/palate**, **polydactyly**, and severe **intellectual disability**.

Q: Which of the following is an autosomal recessive condition?

Ataxia telangiectasia. The correct answer is **Ataxia Telangiectasia (AT)**. This is a multisystem disorder caused by a mutation in the **ATM gene** located on chromosome 11q22.3. It follows an **autosomal recessive (AR)** inheritance pattern [1]. The ATM protein is crucial for repairing double-stranded DNA breaks; its deficiency leads to progressive cerebellar ataxia, oculocutaneous telangiectasia, and severe immunodeficiency [1]. **Analysis of Incorrect Options:** * **Peutz-Jeghers Syndrome:** An **autosomal dominant (AD)** condition characterized by hamartomatous polyps in the GI tract and mucocutaneous hyperpigmentation. It is associated with the STK11 gene. * **Neurofibromatosis (Type 1 and 2):** Both types are **autosomal dominant**. NF1 (von Recklinghausen disease) involves chromosome 17, while NF2 involves chromosome 22. * **Tuberous Sclerosis:** An **autosomal dominant** neurocutaneous syndrome (phakomatosis) caused by mutations in TSC1 (hamartin) or TSC2 (tuberin) genes. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for AR Phakomatoses:** While most neurocutaneous syndromes (NF, Tuberous Sclerosis, von Hippel-Lindau) are **Autosomal Dominant**, **Ataxia Telangiectasia** and **Xeroderma Pigmentosum** are the notable **Autosomal Recessive** exceptions [1]. * **Lab Marker:** Patients with AT often show **elevated Alpha-Fetoprotein (AFP)** levels, which is a key diagnostic clue. * **Radiosensitivity:** Due to defective DNA repair, patients with AT are hypersensitive to ionizing radiation (X-rays/CT scans). * **Classic Triad:** Cerebellar ataxia, telangiectasia (spider veins), and recurrent sinopulmonary infections (due to IgA deficiency).

Question 1

Which one of the following is NOT a characteristic feature of an autosomal recessive disorder?

Accepted Answer

Wide variation in phenotype within a family

Answer

Males and females are equally affected

Answer

Parents of an affected child are usually heterozygous carriers

Answer

Display a horizontal pattern in pedigrees

Question 2

Multifactorial inheritance is most likely to play a role in which of the following conditions?

Accepted Answer

Cleft lip

Answer

Marfan's syndrome

Answer

Down's syndrome

Answer

Erythroblastosis fetalis

Question 3

Von Hippel-Lindau disease is associated with all the following except?

Accepted Answer

Hemangioblastomas

Answer

Endolymphatic sac tumors

Answer

Pheochromocytoma

Answer

Islet cell tumors

Question 4

Klinefelter syndrome is associated with all, except:

Accepted Answer

Barr body absent

Answer

Delayed puberty

Answer

Male phenotype

Answer

Azoospermia

Question 5

Which of the following is false regarding Noonan syndrome?

Accepted Answer

It is autosomal recessive.

Answer

It involves mutations in chromosome 12.

Answer

Both males and females are affected.

Answer

Low levels of clotting factors XI and XII are present.

Question 6

Which syndrome is characterized by the occurrence of both colorectal and endometrial cancers?

Accepted Answer

Lynch syndrome

Answer

Cowden syndrome

Answer

Turcot's syndrome

Answer

Juvenile polyposis syndrome

Question 7

What is the diagnosis suggested by the following karyotype?

Accepted Answer

Cri du chat syndrome

Answer

Down's syndrome

Answer

Turner's syndrome

Answer

Patau Syndrome

Question 8

Down's syndrome is associated with mental retardation. Which of the following chromosomal abnormalities are not typically found in Down's syndrome?

Accepted Answer

Deletion of chromosome 21

Answer

Trisomy 21

Answer

Translocation involving chromosome 21 (e.g., t(13,21), t(21,21))

Answer

Mosaicism with trisomy 21

Question 9

Which of the following statements regarding fluorescence in situ hybridization (FISH) is false?

Accepted Answer

In the process, clones are labeled with fluorescent dyes and applied to the metaphase of the cell cycle.

Answer

FISH uses DNA probes that recognize sequences specific to particular chromosomal regions.

Answer

Multiple chromosomes can be detected simultaneously by introducing spectral karyotyping.

Answer

FISH can also be performed on prenatal samples.

Question 10

Which of the following is an autosomal recessive condition?

Accepted Answer

Ataxia telangiectasia

Answer

Peutz-Jeghers syndrome

Answer

Neurofibromatosis

Answer

Tuberous sclerosis

Molecular Pathology — MCQs

Molecular Pathology — MCQs

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