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Question 1. Which inheritance pattern is characterized by the mutation being expressed predominantly in males and transmitted by carrier females? A) Autosomal dominant B) Autosomal recessive C) X-linked recessive D) Mitochondrial Answer: C Explanation: X-linked recessive disorders are primarily expressed in males, as they have only one X chromosome. Carrier females can transmit the mutation to sons, who will be affected. Question 2. In Hardy-Weinberg equilibrium, which factor does NOT contribute to allele frequency stability in a large, random-mating population? A) Mutation B) Genetic drift C) Migration D) Natural selection Answer: B Explanation: Genetic drift causes allele frequency changes in small populations and disrupts Hardy- Weinberg equilibrium. In large populations, drift's effect diminishes, maintaining stability unless other factors intervene. Question 3. Which process involves the synthesis of RNA from a DNA template? A) Translation B) Transcription C) Replication D) Post-translational modification Answer: B Explanation: Transcription is the process where RNA is synthesized from a DNA template, essential for gene expression regulation.
Question 4. Which enzyme kinetically follows Michaelis-Menten kinetics, displaying a hyperbolic relationship between substrate concentration and reaction rate? A) Allosteric enzymes B) Michaelis-Menten enzymes C) Cooperative enzymes D) Irreversible enzymes Answer: B Explanation: Michaelis-Menten enzymes exhibit hyperbolic kinetics, where reaction velocity increases with substrate concentration until saturation. Question 5. In carbohydrate metabolism, which organ is primarily responsible for gluconeogenesis? A) Liver B) Muscle C) Kidney D) Brain Answer: A Explanation: The liver is the main site of gluconeogenesis, producing glucose from non-carbohydrate substrates during fasting states. Question 6. Which organelle is mainly responsible for lipid breakdown via beta-oxidation? A) Mitochondria B) Lysosomes C) Peroxisomes D) Endoplasmic reticulum Answer: C Explanation: Peroxisomes facilitate initial steps of very-long-chain fatty acid beta-oxidation, with mitochondria completing shorter-chain fatty acids' oxidation. Question 7. Which molecular technique involves sequencing DNA by incorporating chain-terminating nucleotides during DNA synthesis?
B) Gain-of-function C) Dominant negative D) Silent mutation Answer: C Explanation: Dominant negative mutations produce an altered protein that counteracts the normal protein's function, often leading to disease. Question 11. Which of the following best describes the concept of phenotypic variability among individuals with the same genotype? A) Penetrance B) Expressivity C) Completeness of penetrance D) Genetic linkage Answer: B Explanation: Expressivity refers to the degree or severity of phenotype expressed by individuals with the same genotype, accounting for variability. Question 12. Epigenetic modifications that typically result in gene silencing include: A) DNA methylation B) Histone acetylation C) Chromatin relaxation D) DNA replication Answer: A Explanation: DNA methylation usually suppresses gene expression by adding methyl groups to cytosines, leading to gene silencing. Question 13. Which inherited disorder is caused by a deficiency in phenylalanine hydroxylase enzyme? A) Maple Syrup Urine Disease B) Phenylketonuria (PKU) C) Homocystinuria
D) Urea Cycle Disorder Answer: B Explanation: PKU results from deficient phenylalanine hydroxylase, leading to accumulation of phenylalanine and neurotoxicity if untreated. Question 14. Maple Syrup Urine Disease is characterized by a defect in the metabolism of which amino acids? A) Phenylalanine and tyrosine B) Leucine, isoleucine, and valine C) Homocysteine and methionine D) Glycine and serine Answer: B Explanation: MSUD involves defective degradation of branched-chain amino acids leucine, isoleucine, and valine, resulting in toxic accumulation. Question 15. Homocystinuria is most commonly caused by deficiency of which enzyme? A) Phenylalanine hydroxylase B) Cystathionine beta-synthase C) Ornithine transcarbamylase D) Glucose- 6 - phosphatase Answer: B Explanation: Homocystinuria typically results from cystathionine beta-synthase deficiency, impairing homocysteine metabolism. Question 16. A deficiency in carbamoyl phosphate synthetase I leads to which disorder? A) Ornithine transcarbamylase deficiency B) Urea Cycle Disorder (UCD) C) Maple Syrup Urine Disease D) Phenylketonuria Answer: B
Question 20. Disorders of sulfur amino acid metabolism include deficiencies in enzymes such as: A) Cystathionine beta-synthase B) Glutaryl-CoA dehydrogenase C) Phenylalanine hydroxylase D) Ornithine transcarbamylase Answer: A Explanation: Deficiencies in enzymes like cystathionine beta-synthase impair sulfur amino acid metabolism, leading to homocystinuria. Question 21. Glucose storage diseases with impaired glycogen breakdown are classified as: A) Glycogen Storage Diseases (GSDs) B) Organic acidemias C) Lipid storage disorders D) Mucopolysaccharidoses Answer: A Explanation: GSDs are caused by enzyme deficiencies impairing glycogen breakdown or synthesis, leading to abnormal glycogen accumulation. Question 22. Which GSD subtype is characterized by a deficiency in glucose- 6 - phosphatase? A) GSD I (Von Gierke disease) B) GSD II (Pompe disease) C) GSD III (Cori disease) D) GSD V (McArdle disease) Answer: A Explanation: GSD I results from G6Pase deficiency, impairing gluconeogenesis and glycogenolysis, causing severe hypoglycemia. Question 23. Galactosemia is primarily caused by deficiency of which enzyme? A) Galactose- 1 - phosphate uridyltransferase
B) Fructose-1,6-bisphosphatase C) Hexokinase D) Lactase Answer: A Explanation: Galactosemia results from GALT deficiency, leading to accumulation of galactose- 1 - phosphate and toxicity. Question 24. Fructose intolerance is caused by deficiency of which enzyme? A) Aldolase B B) Fructose- 1 - phosphate aldolase C) Hexokinase D) Fructose- 6 - phosphatase Answer: A Explanation: Aldolase B deficiency causes hereditary fructose intolerance, leading to accumulation of fructose- 1 - phosphate. Question 25. A disorder of gluconeogenesis involving deficiency of fructose-1,6-bisphosphatase presents with: A) Hypoglycemia and lactic acidosis B) Hyperglycemia and ketonemia C) Elevated uric acid D) Muscle weakness Answer: A Explanation: Fructose-1,6-bisphosphatase deficiency impairs gluconeogenesis, causing hypoglycemia and lactic acidosis during fasting. Question 26. Congenital Disorders of Glycosylation (CDG) primarily affect: A) Protein and lipid glycosylation pathways B) Fatty acid oxidation C) Amino acid transport
Explanation: Niemann-Pick disease involves sphingomyelin accumulation due to sphingomyelinase deficiency. Question 30. Fabry disease results from deficient activity of which enzyme? A) Alpha-galactosidase A B) Beta-glucocerebrosidase C) Arylsulfatase A D) Sphingomyelinase Answer: A Explanation: Fabry disease is caused by alpha-galactosidase A deficiency, leading to accumulation of globotriaosylceramide. Question 31. Zellweger syndrome is classified as a disorder of: A) Peroxisomal biogenesis B) Mitochondrial DNA C) Lysosomal enzyme deficiency D) Lipid storage Answer: A Explanation: Zellweger syndrome results from defective peroxisome formation, impairing fatty acid oxidation and bile acid synthesis. Question 32. X-linked Adrenoleukodystrophy (ALD) involves defective metabolism of: A) Very-long-chain fatty acids B) Sphingomyelin C) Glycogen D) Urea cycle intermediates Answer: A Explanation: ALD impairs peroxisomal beta-oxidation of very-long-chain fatty acids, causing CNS demyelination and adrenal dysfunction.
Question 33. Smith-Lemli-Opitz syndrome is caused by a defect in: A) Cholesterol biosynthesis pathway B) Fatty acid oxidation pathway C) Glycogen synthesis pathway D) Urea cycle Answer: A Explanation: It results from 7-dehydrocholesterol reductase deficiency, impairing cholesterol synthesis essential for development. Question 34. Lysosomal storage disorders affecting mucopolysaccharide degradation include: A) Hurler and Hunter syndromes B) Niemann-Pick and Gaucher diseases C) Fabry and Krabbe diseases D) Pompe and Cystinosis Answer: A Explanation: MPSs involve deficient enzymes degrading glycosaminoglycans, leading to their accumulation. Question 35. Mucopolysaccharidosis type I (Hurler syndrome) is caused by deficiency of which enzyme? A) Alpha-L-iduronidase B) Iduronate sulfatase C) Arylsulfatase A D) Beta-glucocerebrosidase Answer: A Explanation: Hurler syndrome results from alpha-L-iduronidase deficiency, leading to accumulation of dermatan and heparan sulfate. Question 36. Pompe disease, a lysosomal storage disorder, is due to deficiency of which enzyme? A) Acid alpha-glucosidase B) Sphingomyelinase
Explanation: MELAS involves mitochondrial dysfunction causing stroke-like episodes, lactic acidosis, and epilepsy, but not retinitis pigmentosa. Question 40. A deficiency in Coenzyme Q10 affects which mitochondrial process? A) Electron transport chain B) Krebs cycle C) Fatty acid synthesis D) Glycolysis Answer: A Explanation: Coenzyme Q10 is essential in the electron transport chain, facilitating electron transfer between complexes. Question 41. Which of the following is a characteristic feature of acute intermittent porphyria? A) Photosensitivity B) Neurovisceral symptoms with elevated porphobilinogen in urine C) Hemolytic anemia D) Hepatosplenomegaly Answer: B Explanation: AIP presents with neurovisceral symptoms and elevated urinary porphobilinogen during attacks. Question 42. Congenital erythropoietic porphyria (CEP) is distinguished by: A) Photosensitivity and hemolytic anemia B) Neurovisceral crises C) Asymptomatic carriers only D) Elevated serum ferritin Answer: A Explanation: CEP causes photosensitivity, hemolytic anemia, and skin fragility due to uroporphyrinogen III synthase deficiency.
Question 43. Porphyria cutanea tarda (PCT) mainly involves accumulation of: A) Uroporphyrinogen B) Coproporphyrinogen C) Protoporphyrin IX D) Hemin Answer: A Explanation: PCT results from uroporphyrinogen decarboxylase deficiency, leading to uroporphyrin accumulation causing cutaneous photosensitivity. Question 44. Lesch-Nyhan syndrome is caused by deficiency of which enzyme? A) Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) B) Adenosine deaminase (ADA) C) Xanthine oxidase D) Purine nucleoside phosphorylase Answer: A Explanation: Lesch-Nyhan syndrome involves HGPRT deficiency, impairing purine salvage and leading to uric acid overproduction. Question 45. ADA deficiency leads to: A) Severe combined immunodeficiency (SCID) B) Gout C) Lesch-Nyhan syndrome D) Mitochondrial myopathy Answer: A Explanation: ADA deficiency causes SCID by impairing lymphocyte development due to toxic accumulation of deoxyadenosine. Question 46. Hemochromatosis is primarily characterized by excessive accumulation of: A) Iron B) Copper
Explanation: Mutations in the HFE gene are the most common cause of hereditary hemochromatosis, affecting iron regulation. Question 50. Creatine synthesis involves which amino acids? A) Arginine, glycine, and methionine B) Leucine, isoleucine, and valine C) Phenylalanine and tyrosine D) Serine and threonine Answer: A Explanation: Creatine biosynthesis requires arginine, glycine, and methionine, essential for energy storage in muscle and brain. Question 51. Disorders of neurotransmitter metabolism such as BH4 deficiency primarily affect which neurotransmitter? A) Dopamine B) Serotonin C) GABA D) Acetylcholine Answer: A Explanation: BH4 is a cofactor for dopamine synthesis; deficiency impairs dopamine and other neurotransmitter production. Question 52. Disorders of vitamin B12 metabolism include deficiency of which enzyme? A) Methylmalonyl-CoA mutase B) Cobalamin reductase C) Transketolase D) Pyruvate carboxylase Answer: B Explanation: Cobalamin reductase deficiency impairs vitamin B12 activation, affecting methylation and methylmalonyl-CoA mutase activity.
Question 53. Which biochemical technique is most suitable for detecting small molecules like amino acids and organic acids? A) Mass spectrometry B) Electrophoresis C) PCR D) Microarray Answer: A Explanation: Mass spectrometry provides sensitive detection and quantification of small molecules such as amino acids and organic acids. Question 54. Tandem mass spectrometry (MS/MS) is widely used in newborn screening because it allows: A) Simultaneous analysis of multiple metabolites B) Sequencing of DNA C) Detection of enzyme activity D) Imaging of tissues Answer: A Explanation: MS/MS enables rapid, simultaneous quantification of various metabolites, making it ideal for newborn screening panels. Question 55. A specimen for biochemical analysis of amino acids is best collected in: A) EDTA tube B) Heparin tube C) Clotted serum tube D) Urine container Answer: A Explanation: EDTA preserves amino acids in plasma for accurate biochemical analysis. Question 56. In enzyme assays, the term "specific activity" refers to:
D) Only those with symptoms Answer: A Explanation: Carrier screening detects heterozygous individuals who may pass the mutation to offspring, important for reproductive planning. Question 60. Pre-implantation genetic diagnosis (PGD) is used in conjunction with: A) In vitro fertilization (IVF) B) Natural conception C) Egg donation D) Surrogacy Answer: A Explanation: PGD involves genetic testing of embryos created via IVF to select unaffected ones for implantation. Question 61. Which of the following best describes the principle of microarray technology? A) Hybridization of DNA fragments to known probes for detecting genetic variations B) Amplification of specific DNA sequences C) Sequencing of entire genomes D) Separation of proteins by size and charge Answer: A Explanation: Microarrays detect genetic variations by hybridizing labeled DNA to immobilized probes representing specific sequences. Question 62. In the context of biochemical genetics, the term "critical value" refers to: A) A laboratory result indicating a life-threatening condition requiring immediate attention B) A result within the reference range C) An assay calibration point D) A standard control value Answer: A
Explanation: Critical values are abnormal results that indicate urgent clinical situations needing prompt intervention. Question 63. Which specimen type is most appropriate for measuring enzyme activity in suspected lysosomal storage disorders? A) Tissue biopsy (e.g., skin fibroblasts) B) Urine sample C) Whole blood D) Saliva Answer: A Explanation: Tissue biopsies, especially fibroblasts, are often used for enzyme assays in lysosomal storage disorders. Question 64. The primary ethical concern regarding incidental findings in genetic testing is: A) Disclosing findings unrelated to the original testing purpose B) Ensuring sample privacy C) Maintaining reagent integrity D) Proper sample storage Answer: A Explanation: Incidental findings may reveal unrelated health risks; ethical considerations involve disclosure and patient autonomy. Question 65. The CLIA regulation primarily requires laboratories to: A) Validate and ensure the accuracy of their tests B) Publish research findings C) Perform genetic counseling D) Register with the CDC Answer: A Explanation: CLIA mandates validation, quality control, and proficiency testing to ensure accurate diagnostic results.
