Genetics and Disease Practice Questions

Q: Which pattern of inheritance of disease is associated with consanguinity?

Autosomal recessive. ***Autosomal recessive*** - Consanguineous relationships increase the likelihood of offspring inheriting **two copies of a rare deleterious recessive allele**, one from each parent [1]. - This occurs because relatives share a greater proportion of their genes, making it more probable that both parents are **heterozygous carriers** for the same recessive disorder. *Autosomal dominant* - In autosomal dominant disorders, only **one copy of the altered gene** is needed to cause the disease, so expression is not typically influenced by consanguinity. - These conditions often manifest in every generation and are not more prevalent with increased shared genetic material. *X-linked recessive* - X-linked recessive disorders primarily affect males, as they only have one X chromosome, and are transmitted by carrier females. - While consanguinity can theoretically increase the carrier rate within a population, its direct impact on the inheritance pattern of an X-linked trait in a single family is less pronounced compared to autosomal recessive conditions. *X-linked dominant* - X-linked dominant disorders are expressed in heterozygous females and hemizygous males, with affected males often having more severe disease. - The inheritance pattern is not significantly influenced by consanguinity, as only one copy of the affected gene on the X chromosome is sufficient for disease manifestation.

Q: Which of the following provide protection against malaria except

PNH. ***PNH*** - **Paroxysmal nocturnal hemoglobinuria (PNH)** is a rare, acquired clonal disorder of hematopoietic stem cells characterized by complement-mediated hemolysis. - It does not offer any known protective advantage against malaria infection; in fact, chronic hemolysis could potentially complicate malaria diagnosis or management. *Thalassemia* - Individuals with **thalassemia traits (heterozygotes)**, particularly alpha-thalassemia, have red blood cells that are more resistant to malarial parasite invasion and growth [1]. - This protection is thought to arise from altered red cell morphology, reduced parasite multiplication, and enhanced clearance of infected cells. *Sickle cell anemia* - The **heterozygous state (sickle cell trait)** provides significant protection against severe malaria, as the altered hemoglobin S in red blood cells inhibits parasite growth and promotes early clearance of infected cells [1], [2]. - Although the homozygous state (sickle cell anemia) can be severe, even carriers benefit from reduced malaria susceptibility. *Duffy blood group* - Absence of the **Duffy antigen on red blood cells**, common in West African populations, provides complete protection against infection with **Plasmodium vivax** malaria. - The Duffy antigen receptor is essential for *P. vivax* to invade human red blood cells.

Q: Syndrome which is characterized by 2X chromosomes and 1Y chromosome is:

Klinefelter syndrome. ***Klinefelter syndrome*** - This syndrome is characterized by a **47, XXY karyotype**, meaning individuals have **two X chromosomes** and one Y chromosome [1]. - It affects males, leading to features such as **small testes**, **infertility**, gynecomastia, and often taller stature [1], [3]. *Turner syndrome* - This syndrome is characterized by a **45, X karyotype**, meaning individuals have only **one X chromosome** and no second sex chromosome [2]. - It affects females, leading to features like **short stature**, a **webbed neck**, and ovarian dysgenesis [2]. *Marfan syndrome* - This is an **autosomal dominant genetic disorder** affecting connective tissue, caused by mutations in the **FBN1 gene**. - It is characterized by **tall stature**, long limbs (arachnodactyly), **cardiovascular abnormalities** (e.g., aortic dissection), and ocular problems (e.g., lens dislocation). *Down syndrome* - This syndrome is caused by **trisomy 21**, meaning individuals have an **extra copy of chromosome 21**. - It is characterized by specific **facial features**, intellectual disability, and an increased risk of certain medical conditions like congenital heart defects.

Q: Malaria protection comes from all Except

Acanthocytosis. ***Acanthocytosis*** - **Acanthocytosis** is characterized by abnormal, spiky red blood cells due to lipid membrane defects and does **not** provide protection against malaria. - While red blood cell abnormalities can sometimes offer malaria resistance, acanthocytosis is not one of these known protective conditions. *Sickle cell anemia* - Individuals with **sickle cell trait (heterozygous)** have red blood cells that are less hospitable to the *Plasmodium falciparum* parasite, providing **significant protection** against severe malaria [2]. - The abnormal hemoglobin in sickle cells can lead to premature destruction of infected red blood cells or inhibit parasite growth. *Thalassemia* - **Thalassemia syndromes**, particularly alpha and beta thalassemia traits, provide a degree of protection against malaria [2]. - The affected red blood cells are less suitable for parasite multiplication, and immune responses may be modulated. *G6PD deficiency* - Individuals with **G6PD deficiency** have red blood cells that are more susceptible to oxidative stress, which can inhibit the growth of malaria parasites [1]. - This deficiency causes premature destruction of infected red blood cells, thereby limiting parasite load and providing **some protection** against severe malaria [1].

Q: Which of the following is a sex linked inherited disease?

G6 PD deficiency. ***G6 PD deficiency*** - **Glucose-6-phosphate dehydrogenase (G6PD) deficiency** is an **X-linked recessive** inherited disorder [1]. - Males are predominantly affected as they have only one X chromosome, and a defective gene on it will manifest the disease. *Hypogammaglobulinemia* - This is a broad term for reduced gamma globulins and can have various genetic causes, including **X-linked agammaglobulinemia (Bruton's agammaglobulinemia)**, which is indeed X-linked. However, without further specification, hypogammaglobulinemia alone doesn't definitively point to a sex-linked inheritance as other forms exist. - Other forms of hypogammaglobulinemia, such as **common variable immunodeficiency (CVID)**, can have autosomal dominant or autosomal recessive inheritance patterns or be sporadic. *Diamond-Blackfan anemia* - This is a rare **congenital hypoplastic anemia** primarily inherited in an **autosomal dominant** pattern, though some cases are sporadic. - It is caused by mutations in ribosomal protein genes, and its inheritance is not typically sex-linked. *Down syndrome* - **Down syndrome** (Trisomy 21) is a **chromosomal disorder** caused by the presence of an extra copy of chromosome 21. - It is not a sex-linked inherited disease because it involves an **autosomal chromosome**, not a sex chromosome (X or Y).

Q: 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?

Autosomal dominant. ***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.

Q: Which one of the following is NOT a contraindication in Porphyria?

High calorie diet. ***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.

Q: A 15 year old child has developed dystonia and poor school grades. Slit examination is shown below. Which is the initial investigation recommended for the patient ?

24 hour urinary copper. ***24 hour urinary copper*** - The image shows **Kayser-Fleischer rings**, which, combined with neurological symptoms (**dystonia, poor school grades**) in a 15-year-old, strongly indicate **Wilson's disease**. - A **24-hour urinary copper** measurement is the most reliable initial investigation to confirm the excessive copper excretion characteristic of Wilson's disease. *Serum ceruloplasmin* - While often **low** in Wilson's disease, ceruloplasmin can be normal in some patients, especially those with isolated neurological symptoms. - It's a useful screening test but **less definitive** than urinary copper excretion for diagnosis. *Serum copper* - **Total serum copper** levels can be misleading in Wilson's disease; they are often low due to decreased ceruloplasmin, but free copper is elevated. - This test alone is **not diagnostic** for Wilson's disease as it doesn't reflect the metabolically active copper. *Liver biopsy* - **Liver biopsy** is the **gold standard** for definitive diagnosis, measuring hepatic copper concentration. - However, it is an **invasive procedure** and usually reserved for cases where non-invasive tests are inconclusive or when genetic testing is unavailable.

Q: 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?

Zinc (reduces copper absorption). ***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].

Q: Which of the following is autosomal dominant in inheritance?

Achondroplasia. ***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 1

Which pattern of inheritance of disease is associated with consanguinity?

Accepted Answer

Autosomal recessive

Answer

Autosomal dominant

Answer

X linked recessive

Answer

X linked dominant

Question 2

Which of the following provide protection against malaria except

Accepted Answer

PNH

Answer

Thalassemia

Answer

Sickle cell anemia

Answer

Duffy blood group

Question 3

Syndrome which is characterized by 2X chromosomes and 1Y chromosome is:

Accepted Answer

Klinefelter syndrome

Answer

Turner syndrome

Answer

Marfan syndrome

Answer

Down syndrome

Question 4

Malaria protection comes from all Except

Accepted Answer

Acanthocytosis

Answer

Sickle cell anemia

Answer

Thalassemia

Answer

G6PD deficiency

Question 5

Which of the following is a sex linked inherited disease?

Accepted Answer

G6 PD deficiency

Answer

Hypogamma globuinemia

Answer

Diamond blackfan disease

Answer

Down syndrome

Question 6

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?

Accepted Answer

Autosomal dominant

Answer

Autosomal recessive

Answer

X linked recessive

Answer

X linked dominant

Question 7

Which one of the following is NOT a contraindication in Porphyria?

Accepted Answer

High calorie diet

Answer

Alcohol

Answer

Norethisterone

Answer

Phenobarbitone

Question 8

A 15 year old child has developed dystonia and poor school grades. Slit examination is shown below. Which is the initial investigation recommended for the patient ?

Accepted Answer

24 hour urinary copper

Answer

Serum ceruloplasmin

Answer

Serum copper

Answer

Liver biopsy

Question 9

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?

Accepted Answer

Zinc (reduces copper absorption)

Answer

Penicillamine (a chelating agent)

Answer

Trientine (a chelating agent)

Answer

Pyridoxine (Vitamin B6)

Question 10

Which of the following is autosomal dominant in inheritance?

Accepted Answer

Achondroplasia

Answer

Hemochromatosis

Answer

Sickle cell disease

Answer

Wiskott Aldrich syndrome

Genetics and Disease — MCQs

Genetics and Disease — MCQs

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