Free practice questions

Free CBG Practice Questions

10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.

Start the free practice test → ★★★★★4.9/5 from 2,400+ candidates · No signup

These 10 free CBG questions are organized by exam domain, so you can see how each part of the Clinical Biochemical Genetics blueprint is tested. Reveal the answer and explanation under each question.

Domain 1: Amino acids (15%) - PKU and hyperphenylalaninemia; Tyrosinemias; Glycine encephalopathy/hyperglycinemia; MSUD and disorders of branched-chain amino acids; Homocystinuria/disorders of sulfur amino acids and re-methylation; Urea cycle defects; Other/Serine

Question 1

A newborn has persistent vomiting, respiratory alkalosis, and ammonia of 260 µmol/L. Plasma amino acids show markedly elevated citrulline. Which diagnosis best fits?

ACitrullinemia type I due to argininosuccinate synthetase deficiency BPhenylalanine hydroxylase deficiency CMaple syrup urine disease DTyrosinemia type I

Show answer & explanation

Correct answer: A - Citrullinemia type I due to argininosuccinate synthetase deficiency

Domain 2: Organic acids (12%) - Methylmalonic acidemia (excluding cobalamin defects) and propionic acidemia; 3-MCC deficiency and other C5OH-related disorders including 3-MCC deficiency and other C5OH-related disorders; IVA and other C5-related disorders; Glutaric acidemia type I; Disorders of ketone body metabolism (HMG-CoA lyase, SCOT); Other including Glutathione synthetase deficiency, ECHS1, and 3-methylglutaconic aciduria non-type 1

Question 2

Urine organic acids show increased glutaric acid and 3-hydroxyglutaric acid after neurologic deterioration. Which enzyme is deficient?

AIsovaleryl-CoA dehydrogenase BPropionyl-CoA carboxylase CGlutaryl-CoA dehydrogenase DMethylmalonyl-CoA mutase

Show answer & explanation

Correct answer: C - Glutaryl-CoA dehydrogenase

Domain 3: Cofactors (7%) - Cobalamin; Biotin; Molybdenum; Folate; Pyridoxine; Biopterin; Other including riboflavin, niacin, and thiamine

Question 3

Which cofactor deficiency can cause multiple carboxylase deficiency?

AFolate deficiency BBiotin deficiency CPyridoxine deficiency DCobalamin deficiency

Show answer & explanation

Correct answer: B - Biotin deficiency

Domain 5: Lipids (13%) - Fatty acid oxidation disorders including short-chain, medium-chain, long-chain, and multiple acyl-CoA dehydrogenase deficiency (GA2); Hyperlipidemias including Tangier disease and other; Disorders of cholesterol metabolism including Smith-Lemli-Opitz, Niemann-Pick C, and other bile acid disorders

Question 4

A newborn screen shows elevated C8 acylcarnitine. Which disorder should be considered first?

AVery-long-chain acyl-CoA dehydrogenase deficiency BMedium-chain acyl-CoA dehydrogenase deficiency CMultiple acyl-CoA dehydrogenase deficiency DPrimary carnitine transporter deficiency

Show answer & explanation

Correct answer: B - Medium-chain acyl-CoA dehydrogenase deficiency

Domain 6: Lysosomes (12%) - Mucopolysaccharidoses including Type I, Type II, Type III, Type IV, Type VI, and Type VII; Sphingolipidoses including Gaucher disease, Fabry disease, GM2 gangliosidoses including Tay-Sachs disease and variants and Sandhoff disease, Krabbe disease, Niemann Pick types A and B, GM1 gangliosidosis, and other; Multiple enzyme deficiencies including Mucolipidoses ML-II and ML-III, Multiple sulfatase deficiency, and other; Other including Pompe, Cystinosis, and NCL

Question 5

A child has coarse facial features, hepatosplenomegaly, and alpha-L-iduronidase deficiency. Diagnosis?

AMucopolysaccharidosis type I BFabry disease CPompe disease DKrabbe disease

Show answer & explanation

Correct answer: A - Mucopolysaccharidosis type I

Domain 7: Mitochondria (7%) - Mitochondrial myopathies with laboratory findings; Mitochondrial myopathies with Leigh syndrome; Mitochondrial myopathies with adult presentations; Disorders of electron transport chain function and assembly; Mitochondrial DNA mutation disorders; Disorders of mtDNA maintenance; Mitochondrial DNA depletion syndromes; Other including MELAS

Question 6

Which finding most directly supports a mitochondrial respiratory chain disorder?

AElevated phenylalanine BElevated succinylacetone CAbnormal oxidative phosphorylation studies DElevated very-long-chain fatty acids

Show answer & explanation

Correct answer: C - Abnormal oxidative phosphorylation studies

Domain 9: Purines and pyrimidines (3%) - Purine disorders including Lesch-Nyhan disease, Adenosine deaminase deficiency, and other; Pyrimidine disorders including UMP synthase deficiency and other

Question 7

A male infant has self-injurious behavior and elevated uric acid. Which disorder is most likely?

AAdenosine deaminase deficiency BUMP synthase deficiency CMitochondrial depletion syndrome DLesch-Nyhan disease

Show answer & explanation

Correct answer: D - Lesch-Nyhan disease

Domain 10: Transport (3%) - Dibasic aminoaciduria including cystinuria and lysinuric protein intolerance; Other amino acid transport disorders; Glucose; Carnitine; Other

Question 8

Urine amino acid analysis shows markedly increased cystine with recurrent stones. Which defect is responsible?

ADibasic amino acid transport defect BGlucose transporter defect CCarnitine transport defect DMitochondrial protein import defect

Show answer & explanation

Correct answer: A - Dibasic amino acid transport defect

Domain 13: Metals (3%) - Copper including Wilson disease, Menkes disease, and other; Iron; Zinc; Other

Question 9

Developmental delay with hypopigmentation and abnormal hair microscopy suggests impaired copper transport. Diagnosis?

AWilson disease BMenkes disease CZinc disorder DIron disorder

Show answer & explanation

Correct answer: B - Menkes disease

Domain 14: Laboratory (8%) - QA/QC; Artifact; Techniques; Regulations

Question 10

A laboratory discovers abnormal results caused by delayed specimen processing before analysis. This is best classified as:

AAnalytical imprecision BPost-analytic reporting error CBiological variation DPre-analytic artifact

Show answer & explanation

Correct answer: D - Pre-analytic artifact

The rest of the CBG blueprint

The CBG exam also covers these domains. Drill them in the full free practice test:

Domain 4: Carbohydrates (10%) - Glycogenoses (except GSD II [see LSD]); Disorders of glycolysis; Disorders of gluconeogenesis including fructose-1,6-bisphosphatase deficiency; Disorders of Galactose metabolism; Disorders of fructose metabolism; Congenital disorders of glycosylation; Other including pentose phosphate
Domain 8: Peroxisomes (3%) - Biogenesis disorders including Zellweger syndrome; Single-enzyme disorders including X-linked adrenoleukodystrophy; Other including Refsum - infantile
Domain 11: Creatine 1% of exam
Domain 12: Neurotransmitters (2%) - Succinic semialdehyde dehydrogenase (SSADH) deficiency; Disorders of dopamine synthesis; Other including GABA metabolism
Domain 15: Other disease category 3% of exam

That's 10 of 1,030

The full bank has 1,020 more CBG questions with explanations.

Continue in the free practice test →

View plans