Genetic Disorders and Biochemical Pathology Practice Questions

Q: Which of the following statements about 21-Hydroxylase deficiency is false?

It leads to male pseudohermaphroditism.. ***It leads to male pseudohermaphroditism.*** - **21-Hydroxylase deficiency** does not lead to male pseudohermaphroditism; instead, it causes **virilization in females** (female pseudohermaphroditism) due to increased androgen production. - Males with 21-hydroxylase deficiency typically present with **salt-wasting crises** or **premature pubarche**, but their internal and external genitalia are normal. *It is the most common cause of congenital adrenal hyperplasia.* - This statement is **true**. **21-hydroxylase deficiency** accounts for approximately 90-95% of all cases of congenital adrenal hyperplasia (CAH) [1]. - Its prevalence and significant role in cortisol and aldosterone synthesis pathways make it the predominant form of the disorder [1]. *It is inherited in an autosomal recessive manner.* - This statement is **true**. 21-hydroxylase deficiency is caused by mutations in the **CYP21A2 gene**, which is inherited in an **autosomal recessive pattern**. - Both parents must be carriers for a child to be affected, with each child having a 25% chance of inheriting the disorder. *It leads to female pseudohermaphroditism.* - This statement is **true**. In affected females, the deficiency of 21-hydroxylase shunts steroid precursors towards the **androgen pathway**, leading to excess adrenal androgens. - This excess androgen exposure *in utero* causes **virilization** of external genitalia, resulting in varying degrees of **ambiguous genitalia** (female pseudohermaphroditism).

Q: Pedigree analysis chart is a tool used for which of the following purposes?

Used to see genetic transmission. ***Used to see genetic transmission*** - A **pedigree chart** is a visual representation of biological relationships and genetic traits across multiple generations of a family. - It helps determine the **inheritance pattern** of a particular trait or disease within a family, such as autosomal dominant, recessive, or X-linked. *Used for growth monitoring* - **Growth monitoring** typically involves plotting an individual's weight, height, and head circumference on growth charts over time. - While family data might be considered, a pedigree chart is not the primary tool for directly monitoring an individual's physical growth. *To assess side effects during chemotherapy* - Assessing **side effects during chemotherapy** involves clinical evaluations, laboratory tests (e.g., blood counts, organ function tests), and patient self-reporting. - A pedigree chart provides information about family history and genetic predisposition, not direct monitoring of treatment side effects. *To assess developmental delay in infants* - **Developmental delay assessment** involves observing a child's milestone achievement in areas like motor skills, language, and cognition, often using standardized screening tools. - While some developmental delays can have genetic causes that might be highlighted in a pedigree, the chart itself does not directly assess developmental progress.

Q: What is the metabolic defect in primary oxaluria type II?

D Glycerate dehydrogenase. ***D Glycerate dehydrogenase*** - Primary oxaluria type II (PH2) specifically results from a deficiency in the enzyme **D-glycerate dehydrogenase** (also known as glyoxylate reductase/hydroxypyruvate reductase). - This deficiency leads to the accumulation of **L-glyceric acid** and **oxalate**, causing kidney stones and kidney failure. *Glycine cleavage system* - Defects in the glycine cleavage system are associated with **nonketotic hyperglycinemia**, a condition involving high levels of glycine. - This defect does not primarily cause the accumulation of oxalate. *Alanine glyoxalate amino transferase* - A deficiency in **alanine-glyoxylate aminotransferase (AGT)** is the underlying defect in **primary oxaluria type I (PH1)**. - PH1 is the most common and severe form of primary hyperoxaluria, leading to increased oxalate production. *Excess vitamin C* - While **excessive vitamin C intake** can contribute to increased urinary oxalate excretion in some individuals, it is not a genetic metabolic defect. - It is an exogenous factor, not an intrinsic enzyme deficiency causing primary hyperoxaluria.

Q: Inheritance of Huntington's disease is

Autosomal Dominant. ***AD*** - Huntington's chorea is inherited in an **autosomal dominant** manner, meaning only one copy of the mutated gene is sufficient to cause the disorder [1]. - The disease typically manifests in mid-adulthood, with progressively worsening movement disorders and cognitive decline [1]. *XR* - X-linked recessive disorders typically affect **males** and can be transmitted by carrier females; this is not the case for Huntington's chorea. - The inheritance pattern does not align with the typical clinical presentation of Huntington's, which does not show a gender bias. *XD* - X-linked dominant disorders often affect both sexes, but their inheritance pattern does not describe Huntington's chorea. - Symptoms and gene affected are clearly linked with **autosomal dominant** inheritance, not X-linked dominant. *AR* - Autosomal recessive conditions typically require two copies of the mutated gene, which is not applicable to Huntington's chorea. - This pattern generally leads to earlier onset conditions and significantly different clinical presentations than those observed in Huntington's. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 149-150.

Q: Which one of the following disorders is not X-linked recessive?

Charcot-Marie-Tooth disease. **Charcot-Marie-Tooth disease** - Charcot-Marie-Tooth disease encompasses a group of **hereditary neuropathies** that are most commonly inherited in an **autosomal dominant** pattern, though autosomal recessive and X-linked forms exist, but the dominant form is the most prevalent. - Its diverse genetic basis means it's not exclusively an X-linked recessive disorder. *Lesch-Nyhan syndrome* - This is an **X-linked recessive** disorder caused by a deficiency of the enzyme **hypoxanthine-guanine phosphoribosyltransferase (HGPRT)**. - It is characterized by **hyperuricemia**, neurological dysfunction, and self-mutilating behavior. *Hunter syndrome* - Hunter syndrome (Mucopolysaccharidosis Type II) is an **X-linked recessive** lysosomal storage disorder [1]. - It results from a deficiency of the enzyme **iduronate-2-sulfatase** [1]. *Fragile-X syndrome* - Fragile-X syndrome is an **X-linked disorder** and is the most common inherited cause of intellectual disability. - It is caused by an expansion of a **CGG trinucleotide repeat** in the FMR1 gene.

Q: Lysosomal transport defect is seen in which of the following conditions?

Cystinosis. ***Cystinosis*** - Cystinosis is characterized by **lysosomal transport defects** leading to the accumulation of cystine within lysosomes. - This condition results in **multisystemic involvement**, primarily affecting the kidneys and eyes, due to the inability to effectively transport cystine out of the lysosomes. *Metachromatic leukosytrophy* - Caused by deficiency of the **enzyme arylsulfatase A**, leading to sulfatide accumulation in lysosomes [1]. - It primarily affects the **nervous system** and is not primarily linked to a defect in lysosomal transport. *Goucher's disease* - Results from a deficiency of the enzyme **glucocerebrosidase**, leading to glucocerebroside accumulation [1]. - It mainly affects the **spleen, liver, and bone marrow**, rather than a generalized lysosomal transport defect. *Tay Sach's disease* - Caused by a deficiency in the **enzyme hexosaminidase A**, leading to GM2 ganglioside accumulation in neurones [1]. - This condition primarily affects the **nervous system** and does not involve a defect in lysosomal transport [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 159-164.

Q: Biochemical etiology of Alzheimer's disease relates to:

Acetylcholine. ***Acetylcholine*** - Alzheimer's disease is significantly associated with a **reduction in cholinergic neuronal activity** in the brain, impacting memory and learning. - Medications for Alzheimer's disease often aim to **increase acetylcholine levels** or prevent its breakdown (e.g., cholinesterase inhibitors). *Dopamine* - **Dopamine deficits** are primarily associated with **Parkinson's disease**, affecting motor control and movement. - While dopamine may play a minor role, it is **not considered the primary biochemical etiology** of Alzheimer's. *GABA* - **GABA (gamma-aminobutyric acid)** is the main inhibitory neurotransmitter in the brain and is often associated with anxiety disorders and epilepsy. - While GABAergic system changes can occur in Alzheimer's, they are **secondary to the primary cholinergic dysfunction**. *Serotonin* - **Serotonin** is widely known for its role in mood, sleep, and appetite regulation, and its imbalances are linked to depression and anxiety. - While some **serotonergic changes** can be observed in Alzheimer's disease, the primary biochemical deficit is not serotonin.

Question 1

Which of the following statements about 21-Hydroxylase deficiency is false?

Accepted Answer

It leads to male pseudohermaphroditism.

Answer

It leads to female pseudohermaphroditism.

Answer

It is the most common cause of congenital adrenal hyperplasia.

Answer

It is inherited in an autosomal recessive manner.

Question 2

Pedigree analysis chart is a tool used for which of the following purposes?

Accepted Answer

Used to see genetic transmission

Answer

Used for growth monitoring

Answer

To assess side effects during chemotherapy

Answer

To assess developmental delay in infants

Question 3

What is the metabolic defect in primary oxaluria type II?

Accepted Answer

D Glycerate dehydrogenase

Answer

Glycine cleavage system

Answer

Alanine glyoxalate amino transferase

Answer

Excess vitamin C

Question 4

Inheritance of Huntington's disease is

Accepted Answer

Autosomal Dominant

Answer

X-Linked Recessive

Answer

Autosomal Recessive

Answer

X-Linked Dominant

Question 5

Which one of the following disorders is not X-linked recessive?

Accepted Answer

Charcot-Marie-Tooth disease

Answer

Lesch-Nyhan syndrome

Answer

Hunter syndrome

Answer

Fragile-X syndrome

Question 6

Lysosomal transport defect is seen in which of the following conditions?

Accepted Answer

Cystinosis

Answer

Gaucher's disease

Answer

Metachromatic leukodystrophy

Answer

Tay-Sachs disease

Question 7

Biochemical etiology of Alzheimer's disease relates to:

Accepted Answer

Acetylcholine

Answer

Dopamine

Answer

GABA

Answer

Serotonin

Genetic Disorders and Biochemical Pathology — MCQs

Genetic Disorders and Biochemical Pathology — MCQs

On this page

Practice by Chapter

Want unlimited practice?