Molecular Pathology Practice Questions

Q: Analyze the provided pedigree chart to identify the underlying genetic disease.

Crouzon syndrome. ***Crouzon syndrome*** - Shows **autosomal dominant inheritance** pattern with multiple generations affected, both sexes involved, and approximately **50% of offspring** affected. - Exhibits **father-to-son transmission**, which is characteristic of autosomal dominant conditions and excludes X-linked inheritance. *Sickle cell anaemia* - Follows **autosomal recessive inheritance** where typically only one generation is affected with unaffected parents having affected children. - Would require **both parents to be carriers** and show a **25% recurrence risk** in offspring, not the pattern seen in the pedigree. *Diabetes insipidus* - Most forms are **acquired** rather than inherited, and when hereditary, usually show **autosomal dominant** or **X-linked recessive** patterns. - **Nephrogenic diabetes insipidus** (X-linked) would show male predominance with no father-to-son transmission, inconsistent with this pedigree. *Hunter syndrome* - Exhibits **X-linked recessive inheritance** with affected males and carrier females, showing a distinctive pattern. - Would demonstrate **no father-to-son transmission** and predominantly affect males through carrier mothers, unlike the pedigree shown.

Q: Which gene mutation is seen in Marfan syndrome?

Fibrillin-1 gene. **Explanation:** **Marfan Syndrome** is an autosomal dominant connective tissue disorder characterized by mutations in the **FBN1 gene** located on **chromosome 15q21.1**. This gene encodes **Fibrillin-1**, a glycoprotein essential for the formation of elastic fibers in the extracellular matrix. Fibrillin-1 also plays a critical role in sequestering Transforming Growth Factor-beta (TGF-β); its deficiency leads to excess TGF-β signaling, resulting in the characteristic overgrowth of long bones and weakening of connective tissues. **Analysis of Incorrect Options:** * **FGFR-3 gene (Option B):** Mutations in the Fibroblast Growth Factor Receptor 3 gene lead to **Achondroplasia**, the most common cause of dwarfism. * **COL1A1 gene (Option C):** Mutations in Collagen Type 1 (COL1A1/COL1A2) are associated with **Osteogenesis Imperfecta**, characterized by bone fragility and blue sclera. * **Fibrillin-2 gene (Option D):** Mutations in the FBN2 gene (chromosome 5) cause **Beals Syndrome** (Congenital Contractural Arachnodactyly), which mimics Marfanoid features but presents with multiple joint contractures and "crumpled" ears. **High-Yield Clinical Pearls for NEET-PG:** * **Skeletal:** Arachnodactyly (long fingers), pectus excavatum/carinatum, and scoliosis. * **Ocular:** **Ectopia lentis** (dislocation of the lens), typically **superior-temporal** (upward). * **Cardiovascular:** The most serious complications are **Aortic Root Dilation** and Aortic Dissection. * **Diagnostic Criteria:** Based on the **Revised Ghent Nosology**, focusing on FBN1 mutation, aortic root aneurysm, and ectopia lentis.

Question 1

Analyze the provided pedigree chart to identify the underlying genetic disease.

Accepted Answer

Crouzon syndrome

Answer

Sickle cell anaemia

Answer

Diabetes insipidus

Answer

Hunter syndrome

Question 2

What is the most common tumor in females with tuberous sclerosis?

Accepted Answer

Angiomyolipoma

Answer

Rhabdomyosarcoma

Answer

Pulmonary lymphangioleiomyomatosis

Answer

Optic glioma

Question 3

What is a Leiden mutation?

Accepted Answer

Mis-sense mutation

Answer

Frame shift mutation

Answer

Tri nucleotide repeat mutation

Answer

Non-sense mutation

Question 4

Aneuploidy is seen with all except:

Accepted Answer

DiGeorge syndrome

Answer

Trisomy of chromosome 18 and 13

Answer

Trisomy 21

Answer

Klinefelter syndrome

Question 5

A 20-year-old woman has a Robertsonian translocation involving chromosome 21 and a second acrocentric chromosome. What is the theoretic likelihood of a functional trisomy 21 if one of her ova is fertilized by a normal sperm?

Accepted Answer

1 in 3

Answer

1 in 1

Answer

1 in 2

Answer

1 in 4

Question 6

Trisomy 13 is identified as:

Accepted Answer

Patau's syndrome

Answer

Edward's syndrome

Answer

Down's syndrome

Answer

Klinefelter's syndrome

Question 7

Which gene mutation is seen in Marfan syndrome?

Accepted Answer

Fibrillin-1 gene

Answer

FGFR-3 gene

Answer

COL1A1 gene

Answer

Fibrillin-2 gene

Question 8

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

Accepted Answer

Hemangioblastomas

Answer

Endolymphatic sac tumors

Answer

Pheochromocytoma

Answer

Islet cell tumors

Question 9

What is the function of the FMR1 protein?

Accepted Answer

It is coded by the FMR1 gene which has the (5′-CGG-3′) n repeat segments.

Answer

It is expressed in fragile X-associated mental retardation.

Answer

It is normally found in the brain and ovaries.

Answer

When defective, it is not sufficient to cause the fragile X-associated mental retardation syndrome.

Question 10

Which of the following statements regarding Down syndrome is FALSE?

Accepted Answer

It is the most common trisomy in humans.

Answer

It occurs due to meiotic non-disjunction of chromosome 21.

Answer

It is characterized by Trisomy 21.

Answer

The most common congenital heart defect (CHD) associated with it is an endocardial cushion defect.

Molecular Pathology — MCQs

Molecular Pathology — MCQs

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