Genetics and Disease — MCQs
On this page
Not true about blue sclera
A patient taken for surgery was given suxamethonium, following which his body temperature began to rise quickly. Along with this he also developed masseter spasm, tachycardia and arrhythmia. An ABG analysis also revealed that he has hypoxia, hypercarbia and acidosis. What is the mode of inheritance of the condition described above?
Which one of the following statements is false regarding chronic granulomatous disease?
Which one of the following is NOT a contraindication in Porphyria?
History of dislike for sweet food items is typically present in:
Transplantation between identical twins-
All of the following are associated with malignancy except:
A 60-year-old man presents with choreoathetosis. On examination, Kayser-Fleischer rings are seen in the cornea. What is the initial treatment of choice for this condition?
Which of the following is autosomal dominant in inheritance?
Which of the following disorders presents with repeated catalase positive infections?
Genetics and Disease Indian Medical PG Practice Questions and MCQs
Question 241: Not true about blue sclera
- A. Blue colour is produced by underlying uveal pigment
- B. Seen in osteogenesis imperfecta
- C. Not seen in Ehlers-Danlos syndrome
- D. Seen in Marfan's syndrome (Correct Answer)
Explanation: ***Seen in Marfan's syndrome*** - **Blue sclera** is not a characteristic feature of **Marfan's syndrome**. - Marfan's syndrome is primarily associated with **connective tissue abnormalities** affecting the heart, blood vessels, eyes (lens dislocation), and skeleton, but not typically blue sclera. *Blue colour is produced by underlying uveal pigment* - The blue appearance of the sclera is due to the **thinness of the scleral collagen**, allowing the underlying **dark choroidal pigment** (part of the uvea) to be more visible. - This transparency effect is sometimes enhanced by the presence of **sub-scleral fat**, which reflects blue light. *Seen in osteogenesis imperfecta* - **Osteogenesis imperfecta** is a genetic disorder characterized by **brittle bones** and **blue sclera**. - The blue color is due to the **thinning of the sclera**, allowing the underlying choroidal veins to show through. *Not seen in Ehlers-Danlos syndrome* - **Blue sclera** can indeed be a feature of **Ehlers-Danlos syndrome**, particularly in types associated with **collagen defects** [1]. - Like osteogenesis imperfecta, the thinned sclera allows the underlying **choroid** to become visible, creating the blue hue [1].
Question 242: A patient taken for surgery was given suxamethonium, following which his body temperature began to rise quickly. Along with this he also developed masseter spasm, tachycardia and arrhythmia. An ABG analysis also revealed that he has hypoxia, hypercarbia and acidosis. What is the mode of inheritance of the condition described above?
- A. Autosomal recessive
- B. X linked recessive
- C. X linked dominant
- D. Autosomal dominant (Correct Answer)
Explanation: ***Autosomal dominant*** - This clinical scenario describes **malignant hyperthermia**, a life-threatening pharmacological emergency triggered by certain anesthetic agents like **suxamethonium** and volatile anesthetics. - Malignant hyperthermia is most commonly caused by mutations in the **RYR1 gene**, which codes for the ryanodine receptor, and is inherited in an **autosomal dominant** pattern [1]. *Autosomal recessive* - While some genetic conditions are inherited in an autosomal recessive manner, **malignant hyperthermia** is characteristically autosomal dominant. - Autosomal recessive disorders typically require two copies of the mutated gene (one from each parent) to manifest, which is not the primary inheritance pattern for this condition. *X linked recessive* - **X-linked recessive** inheritance primarily affects males, with females usually being carriers, and is not the typical mode of inheritance for **malignant hyperthermia**. - Conditions like Duchenne muscular dystrophy exemplify X-linked recessive inheritance. *X linked dominant* - **X-linked dominant** disorders affect both males and females, but often with differing severity or presentation, and are not the characteristic inheritance pattern for **malignant hyperthermia**. - While rare, X-linked dominant conditions like Rett syndrome have distinct inheritance patterns.
Question 243: Which one of the following statements is false regarding chronic granulomatous disease?
- A. It is an autosomal dominant disease (Correct Answer)
- B. Recurrent staphylococcal infections are usual in this disease
- C. Nitro blue tetrazolium test is useful for screening
- D. It is characterized by abnormal bacterial phagocytosis
Explanation: ### It is an autosomal dominant disease - The most common and severe form of chronic granulomatous disease (CGD) is inherited as an **X-linked recessive disorder**. - There are also autosomal recessive forms, but **never autosomal dominant inheritance**. *Recurrent staphylococcal infections are usual in this disease* - Patients with CGD are particularly susceptible to infections with **catalase-positive organisms** like *Staphylococcus aureus* because their phagocytes cannot effectively kill these microbes. - This is due to a defect in the **NADPH oxidase enzyme**, which impairs the production of reactive oxygen species essential for bacterial killing [1]. *Nitro blue tetrazolium test is useful for screening* - The **nitroblue tetrazolium (NBT) test** is a traditional screening method for CGD, as it detects the ability of phagocytes to produce a **respiratory burst** and reduce NBT dye [1]. - In CGD, the NBT dye remains yellow (unreduced) due to the absence or deficiency of NADPH oxidase activity. *It is characterized by abnormal bacterial phagocytosis* - CGD is characterized by **defective intracellular killing of phagocytosed bacteria and fungi**, not abnormal phagocytosis itself. - Phagocytes (neutrophils, macrophages) can engulf microbes normally, but they fail to produce the **oxidative burst** necessary to destroy them [1].
Question 244: Which one of the following is NOT a contraindication in Porphyria?
- A. Alcohol
- B. Norethisterone
- C. High calorie diet (Correct Answer)
- D. Phenobarbitone
Explanation: ***High calorie diet*** - A **high caloric intake**, especially with **carbohydrates**, is often used as a treatment strategy for acute porphyric attacks. This approach helps to suppress **ALAS1 activity**, thereby reducing the synthesis of porphyrin precursors that accumulate in porphyria. - Maintaining adequate nutrition is beneficial in general and does not exacerbate porphyria; rather, **fasting** and **starvation** can precipitate acute attacks by increasing **heme synthesis** and porphyrin precursor production [1]. *Alcohol* - Alcohol is a well-known **precipitating factor** for acute porphyria attacks [1]. It induces **hepatic cytochrome P450 enzymes**, which in turn stimulate **ALAS1 activity**—the rate-limiting enzyme in heme synthesis, leading to an overproduction of porphyrin precursors [2]. - Its metabolism can also deplete **hepatic glucose stores**, contributing to a state that mimics starvation, further exacerbating the disease. *Norethisterone* - **Norethisterone**, a synthetic progesterone, is a potent inducer of **ALAS1 activity** in the liver and is therefore contraindicated in individuals with acute intermittent porphyria (AIP) due to its ability to trigger acute attacks. - Many hormonal contraceptives and steroids can exacerbate porphyria by promoting **heme synthesis**, so they must be avoided or used with extreme caution [1]. *Phenobarbitone* - **Phenobarbitone**, a barbiturate, is a classic example of a drug that is **absolutely contraindicated** in porphyria. It potently induces **hepatic cytochrome P450 enzymes** and significantly upregulates **ALAS1 activity**, leading to a surge in neurotoxic porphyrin precursors [2]. - Its use can precipitate severe and life-threatening attacks of acute porphyria, including neurological symptoms, and should always be avoided in affected individuals.
Question 245: History of dislike for sweet food items is typically present in:
- A. Glycogen storage disease
- B. Diabetes mellitus
- C. Galactosemia
- D. Hereditary fructose intolerance (Correct Answer)
Explanation: ***Hereditary fructose intolerance*** - Patients with hereditary fructose intolerance develop severe symptoms like **nausea, vomiting, abdominal pain, and hypoglycemia** after ingesting fructose, leading to an aversive response and **dislike for sweet food items**. - This aversion is a protective mechanism, as avoiding fructose-containing foods (including many sweets) prevents the accumulation of toxic metabolites due to a deficiency in **hepatic aldolase B**. *Glycogen storage disease* - While glycogen storage diseases can cause hypoglycemia, they typically do not lead to a specific **aversion to sweet foods**. - The primary defect is in **glycogen synthesis or breakdown**, leading to symptoms like hepatomegaly, muscle weakness, and exercise intolerance. *Diabetes mellitus* - Patients with diabetes mellitus often have a **craving for sweet foods** due to uncontrolled blood glucose levels and insulin resistance, rather than a dislike. - The condition is characterized by **hyperglycemia** and may involve polydipsia, polyuria, and polyphagia. *Galactosemia* - Galactosemia involves an inability to metabolize galactose, leading to symptoms such as **vomiting, lethargy, and jaundice** upon milk ingestion [1]. - While patients will avoid milk, their aversion is not generally to all sweet foods, as sweet foods do not always contain galactose [1].
Question 246: Transplantation between identical twins-
- A. Xenograft
- B. Autograft
- C. Isograft (Correct Answer)
- D. Allograft
Explanation: ***Isograft*** - An **isograft** refers to a transplant between **genetically identical individuals**, such as identical twins, thus minimizing immune rejection [1]. - Due to the identical genetic makeup, the recipient's immune system will not recognize the transplanted tissue as foreign, making **immunosuppression unnecessary** [1]. *Xenograft* - A **xenograft** involves transplantation of tissues or organs between **different species**, for example, from a pig to a human. - These grafts typically face severe and rapid **immune rejection** due to significant genetic differences between the donor and recipient species. *Autograft* - An **autograft** is a transplant of tissue from **one part of an individual's body to another part of the same individual**. - This type of graft has no risk of rejection as the tissue is genetically identical to the recipient's own tissue [2]. *Allograft* - An **allograft** is a transplant between **genetically non-identical individuals of the same species**, such as between two non-twin humans. - These grafts always require **immunosuppressive therapy** to prevent rejection due to genetic differences, though rejection rates vary based on HLA matching [1].
Question 247: All of the following are associated with malignancy except:
- A. Down syndrome
- B. Fragile X syndrome (Correct Answer)
- C. Fanconi anemia
- D. Bloom syndrome
Explanation: ***Fragile X syndrome*** - Fragile X syndrome is primarily associated with **intellectual disability** and developmental delays, not an increased risk of malignancy [1]. - It is caused by an expansion of the **CGG repeat** in the FMR1 gene, leading to reduced or absent FMRP protein. *Down syndrome* - Individuals with Down syndrome (Trisomy 21) have a significantly increased risk of developing certain cancers, particularly **acute lymphoblastic leukemia (ALL)** and **acute myeloid leukemia (AML)**. - This increased leukemia risk is several times higher than in the general population. *Fanconi anemia* - Fanconi anemia is a rare genetic disorder characterized by **bone marrow failure** and an increased predisposition to various cancers. - Patients are at a higher risk for **acute myeloid leukemia (AML)** and **myelodysplastic syndromes (MDS)**, as well as head and neck squamous cell carcinomas. *Bloom syndrome* - Bloom syndrome is a very rare genetic disorder associated with an exceptionally high risk of developing a wide range of cancers early in life. - This increased susceptibility is due to **genomic instability** and a high frequency of chromosomal rearrangements.
Question 248: A 60-year-old man presents with choreoathetosis. On examination, Kayser-Fleischer rings are seen in the cornea. What is the initial treatment of choice for this condition?
- A. Penicillamine (a chelating agent)
- B. Zinc (reduces copper absorption) (Correct Answer)
- C. Trientine (a chelating agent)
- D. Pyridoxine (Vitamin B6)
Explanation: ***Zinc (reduces copper absorption)*** - **Zinc** is often the initial treatment of choice, especially in asymptomatic or mildly symptomatic patients, as it works by inducing **metallothionein** in the intestinal cells, which binds copper and prevents its absorption. - This reduces the body's copper load without causing potential side effects associated with intense chelation, making it a safer first-line option. *Penicillamine (a chelating agent)* - **D-penicillamine** is a chelating agent that binds to copper and promotes its excretion; however, it has significant side effects such as **nephrotoxicity** and **bone marrow suppression**. - Its use is generally reserved for patients who cannot tolerate zinc or require more aggressive copper removal. *Trientine (a chelating agent)* - **Trientine** is another copper chelating agent, often preferred over penicillamine due to its better side-effect profile but still considered a more aggressive treatment than zinc. - It is typically used for patients who are unable to tolerate penicillamine or require chelation. *Pyridoxine (Vitamin B6)* - **Pyridoxine (Vitamin B6)** is not a direct treatment for Wilson's disease. - It's mainly used to prevent or treat peripheral neuropathy in patients receiving **isoniazid** or **penicillamine**, as penicillamine can sometimes interfere with B6 metabolism [1].
Question 249: Which of the following is autosomal dominant in inheritance?
- A. Achondroplasia (Correct Answer)
- B. Hemochromatosis
- C. Sickle cell disease
- D. Wiskott Aldrich syndrome
Explanation: ***Achondroplasia*** - This condition is inherited in an **autosomal dominant** pattern, meaning only one copy of the mutated gene is needed to cause the disorder. - It is caused by a mutation in the **FGFR3 gene**, leading to abnormal bone growth and short-limbed dwarfism [1]. *Hemochromatosis* - This condition is primarily inherited in an **autosomal recessive** pattern, meaning two copies of the mutated gene (HFE gene) are required for the disease to manifest. - It leads to excessive iron absorption and organ damage. *Sickle cell disease* - This is an **autosomal recessive** disordertoo. - It results from a mutation in the **HBB gene**, affecting hemoglobin and causing red blood cells to become sickle-shaped. *Wiskott Aldrich syndrome* - This is an **X-linked recessive** disorder, meaning it primarily affects males. - It involves mutations in the **WAS gene**, leading to immunodeficiency, eczema, and thrombocytopenia.
Question 250: Which of the following disorders presents with repeated catalase positive infections?
- A. Chediak higashi syndrome
- B. SCID
- C. X linked hypogammaglobulinemia
- D. CGD (Correct Answer)
Explanation: ***CGD*** - Chronic Granulomatous Disease (CGD) is characterized by a defect in **NADPH oxidase**, preventing phagocytes from producing a **respiratory burst** to kill certain bacteria and fungi. - Patients with CGD are particularly susceptible to infections by **catalase-positive organisms** because these organisms degrade hydrogen peroxide, which CGD phagocytes rely on for killing. *Chediak higashi syndrome* - This syndrome involves defective lysosomal trafficking, leading to impaired neutrophil chemotaxis and degranulation, resulting in recurrent infections, but not specifically to **catalase-positive organisms**. - Other features include **partial albinism**, peripheral neuropathy, and normal respiratory burst. *SCID* - Severe Combined Immunodeficiency (SCID) involves a profound defect in both **T-cell and B-cell immunity**, leading to severe and recurrent infections by a wide range of pathogens, not limited to catalase-positive ones [1]. - Patients typically present in infancy with **failure to thrive**, opportunistic infections, and lack of lymphoid tissue [1]. *X linked hypogammaglobulinemia* - Also known as **Bruton's agammaglobulinemia**, this disorder involves a defect in B-cell maturation, leading to the absence of antibodies and recurrent bacterial infections [1]. - The infections are typically with **encapsulated bacteria** and are not specifically linked to catalase-positive organisms [1].
Practice by Chapter
Principles of Medical Genetics
Practice Questions
Genetic Testing and Counseling
Practice Questions
Single Gene Disorders
Practice Questions
Chromosomal Disorders
Practice Questions
Mitochondrial Diseases
Practice Questions
Pharmacogenomics
Practice Questions
Cancer Genetics
Practice Questions
Genetics of Common Diseases
Practice Questions
Epigenetics and Disease
Practice Questions
Genetic Basis of Developmental Disorders
Practice Questions
Ethical Issues in Medical Genetics
Practice Questions
Gene Therapy and Precision Medicine
Practice Questions
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free