About CBG Exam Prep
An independent practice platform for the Clinical Biochemical Genetics (CBG) exam - real questions across every exam domain, each with a plain-language explanation.
What's on the CBG exam
The Clinical Biochemical Genetics (CBG) exam is organized into 15 knowledge domains. Each domain makes up a different share of the exam, so the most efficient way to prepare is to know where the weight sits and practice accordingly:
- 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
- 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
- Cofactors (7%) — Cobalamin; Biotin; Molybdenum; Folate; Pyridoxine; Biopterin; Other including riboflavin, niacin, and thiamine
- 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
- 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
- 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
- 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
- Peroxisomes (3%) — Biogenesis disorders including Zellweger syndrome; Single-enzyme disorders including X-linked adrenoleukodystrophy; Other including Refsum - infantile
- Purines and pyrimidines (3%) — Purine disorders including Lesch-Nyhan disease, Adenosine deaminase deficiency, and other; Pyrimidine disorders including UMP synthase deficiency and other
- Transport (3%) — Dibasic aminoaciduria including cystinuria and lysinuric protein intolerance; Other amino acid transport disorders; Glucose; Carnitine; Other
- Creatine1% of the exam
- Neurotransmitters (2%) — Succinic semialdehyde dehydrogenase (SSADH) deficiency; Disorders of dopamine synthesis; Other including GABA metabolism
- Metals (3%) — Copper including Wilson disease, Menkes disease, and other; Iron; Zinc; Other
- Laboratory (8%) — QA/QC; Artifact; Techniques; Regulations
- Other disease category3% of the exam
Every practice question on this site is organized across these 15 domains, so your study tracks the real exam structure instead of guesswork. As you answer, the per-domain analytics surface the areas still costing you points, so your review goes where it moves your score.
What we believe good exam prep looks like
Realistic practice beats passive reading. Every question is written to mirror the style and difficulty of the real exam, with a clear explanation of why the right answer is right and the others aren't.
Your weak spots should find you. Domain analytics, mistake review, and re-drilling are built in, so study time goes where it moves your score.
Pricing should be simple. One payment for a fixed access window matched to your exam date. No subscription, no auto-renewal, and 10 free questions to try before you spend anything.
Get in touch
Questions, feedback, or something not working? Email support@boardmentor.study - candidate messages are read and answered.