- What This Cheat Sheet Covers
- The ABMGG Blueprint at a Glance
- Amino Acids and Organic Acids: The Heavy Hitters
- Lipids, Lysosomes, and Carbohydrates
- Small Domains, Big Traps
- The Laboratory Domain: Interpreting the Data
- Pattern Recognition Shortcuts
- Scheduling Your Review by Domain Weight
- What Public Sources Do Not Verify
- Frequently Asked Questions
- MBG means Medical Biochemical Genetics, examined under the American Board of Medical Genetics and Genomics (ABMGG).
- Amino acids carry the most weight at 15%, followed by lipids at 13%.
- Organic acids and lysosomes each account for 12% of the blueprint content.
- Laboratory interpretation is 8% of the blueprint, and it threads through every metabolic domain.
What This Cheat Sheet Covers
This page condenses the ABMGG 2025 Biochemical Genetics Blueprint and Content Codes into a single reference. It is built for candidates in the final stretch of preparation who need a fast refresher on how the exam is organized and which concepts reward memorization versus reasoning. If you are still deciding whether to pursue the credential, start with What Is MBG Certification? and MBG Requirements 2026: Eligibility, Prerequisites & How to Qualify before returning here.
A note on scope: the blueprint is a list of content topics with approximate percentages. It tells you what the exam samples, not how many questions you will see or how they are scored. Treat every percentage below as an approximate emphasis, not a guaranteed question count.
The ABMGG Blueprint at a Glance
The blueprint divides Medical Biochemical Genetics into 15 content domains. The table below lists every domain with its approximate weight. For a deeper narrative treatment of each area, see MBG Exam Domains 2026: Complete Guide to All 15 Content Areas.
| Domain | Content Area | Approx. Weight |
|---|---|---|
| 1 | Amino acids | 15% |
| 2 | Organic acids | 12% |
| 3 | Cofactors | 7% |
| 4 | Carbohydrates | 10% |
| 5 | Lipids | 13% |
| 6 | Lysosomes | 12% |
| 7 | Mitochondria | 7% |
| 8 | Peroxisomes | 3% |
| 9 | Purines and pyrimidines | 3% |
| 10 | Transport | 3% |
| 11 | Creatine | 1% |
| 12 | Neurotransmitters | 2% |
| 13 | Metals | 3% |
| 14 | Laboratory | 8% |
| 15 | Other disease category | 3% |
Reading the weights correctly
Four domains (amino acids, lipids, organic acids, lysosomes) account for roughly half of the blueprint. Add carbohydrates and laboratory, and six domains cover about 70% of the content. That concentration is the single most useful fact on this page for prioritizing review time. It does not mean the remaining domains are ignorable, since a 3% domain can still decide a borderline result.
Amino Acids and Organic Acids: The Heavy Hitters
Together these two domains represent about 27% of the blueprint. Both are built around enzyme pathways, characteristic metabolites, and the clinical presentations that follow from a block.
Domain 1: Amino Acids (15%)
The largest single domain. Expect questions that move between a clinical vignette, a plasma or urine amino acid pattern, the deficient enzyme, and the management logic.
- Phenylalanine and tyrosine pathways, including the distinction between phenylalanine hydroxylase deficiency and cofactor-related hyperphenylalaninemia
- Urea cycle disorders: which enzyme defect produces which pattern of ammonia, glutamine, citrulline, argininosuccinate, and orotic acid
- Branched-chain amino acid catabolism and the maple syrup urine disease pattern
- Homocysteine and methionine metabolism, and how to separate remethylation from transsulfuration defects
- Glycine, serine, and proline-related disorders
Domain 2: Organic Acids (12%)
This domain rewards candidates who can read a urine organic acid profile and name the block. Many organic acidemias share overlapping clinical crises, so the metabolite pattern is the discriminator.
- Propionic and methylmalonic acidemia: shared features, differentiating metabolites, and the role of vitamin B12 responsiveness
- Isovaleric acidemia, glutaric acidemia, and related leucine and lysine catabolism disorders
- Characteristic ketoacidosis, hyperammonemia, and neutropenia associations
- How acute decompensation is recognized and what the biochemical findings imply about the underlying defect
Before test day, be able to say, for each major disorder in these domains, the enzyme, the accumulating metabolite, the typical newborn or early-childhood presentation, and the first-line dietary or pharmacologic principle. If any of the four is missing from your memory, that disorder is not yet exam-ready.
Lipids, Lysosomes, and Carbohydrates
These three domains add up to about 35% of the blueprint. They overlap in an important way: several lysosomal storage disorders involve complex lipids and glycoconjugates, so your lipid and lysosomal knowledge should be studied as a connected system.
Domain 5: Lipids (13%)
Covers fatty acid oxidation, lipoprotein disorders, and cholesterol and bile acid metabolism.
- Fatty acid oxidation defects: the chain-length spectrum, hypoketotic hypoglycemia, and the role of acylcarnitine profiling
- Carnitine cycle and transport defects
- Disorders of cholesterol biosynthesis and their dysmorphology links
- Lipoprotein metabolism and familial lipid disorders
Domain 6: Lysosomes (12%)
Storage disorders reward systematic organization by substrate class.
- Sphingolipidoses, mucopolysaccharidoses, oligosaccharidoses, and glycoproteinoses as separate families
- For each: enzyme, stored substrate, inheritance pattern, hallmark clinical features, and confirmatory testing approach
- Where enzyme replacement or other therapeutic strategies apply, and where they do not
- X-linked versus autosomal recessive patterns, which are easy to confuse under time pressure
Domain 4: Carbohydrates (10%)
Focuses on glycogen storage, galactose, fructose, and disorders of glycosylation.
- Glycogen storage disease types: matching enzyme to organ involvement (liver, muscle, or both)
- Galactosemia and hereditary fructose intolerance: diet triggers and metabolite findings
- Congenital disorders of glycosylation and the transferrin isoform patterns used to screen for them
- Hypoglycemia workups that separate carbohydrate, fatty acid, and hormonal causes
Small Domains, Big Traps
Cofactors (7%), mitochondria (7%), and the seven smallest domains (peroxisomes 3%, purines and pyrimidines 3%, transport 3%, creatine 1%, neurotransmitters 2%, metals 3%, other disease category 3%) are easy to under-prepare. Collectively the seven smallest cover about 18% of the blueprint, which is more than the lipid domain alone.
Cofactors and mitochondria
- Cofactors (7%): Know which vitamins and cofactors support which enzymes, and which disorders are cofactor-responsive. This domain is the natural bridge between amino acids, organic acids, and mitochondrial disease.
- Mitochondria (7%): Focus on oxidative phosphorylation, pyruvate dehydrogenase complex, lactate and pyruvate interpretation, and the clinical heterogeneity of mitochondrial disease.
The seven smallest domains
- Peroxisomes: Zellweger spectrum features, very long chain fatty acid findings, and the biochemical separation of single-enzyme from biogenesis disorders.
- Purines and pyrimidines: Lesch-Nyhan syndrome, adenosine deaminase deficiency, and the uric acid abnormalities that accompany them.
- Transport: Membrane transporter disorders such as cystinuria and related renal or intestinal transport defects.
- Creatine: The three creatine synthesis and transport disorders and how they are distinguished, usually by guanidinoacetate and creatine measurements.
- Neurotransmitters: Disorders of monoamine and GABA metabolism and the cerebrospinal fluid patterns that identify them.
- Metals: Wilson disease, Menkes disease, and iron-related disorders, including the copper and ceruloplasmin logic.
- Other disease category: Items that do not fit a single metabolic class, so expect breadth rather than depth.
Key Takeaway
Do not skip creatine at 1% or neurotransmitters at 2%. These domains contain compact, learnable facts, so a short targeted review can convert them into reliable points with very little study time.
The Laboratory Domain: Interpreting the Data
At 8%, the laboratory domain is the sixth-largest content area, and it influences how you should study every other domain. Biochemical geneticists are expected to interpret test results, not merely recall disease names.
Domain 14: Laboratory (8%)
Think of this domain as the methods and interpretation layer that sits on top of the disease content.
- Newborn screening concepts: how analytes are measured, what a positive screen does and does not mean, and follow-up confirmatory testing
- Tandem mass spectrometry, amino acid analysis, organic acid analysis, and acylcarnitine profiling: what each platform detects
- Enzyme assay principles and the limits of pseudodeficiency and sample handling issues
- Pre-analytic variables such as fasting state, sample type, and stability that can mimic or mask disease
- Molecular testing concepts and how genotype data are integrated with biochemical findings
A reliable habit is to attach a testing method to every disorder you study. For each condition, ask which specimen, which assay, and which pattern would confirm it, and what could produce a false result. That habit makes the laboratory domain a byproduct of your disease review rather than a separate memorization task.
Pattern Recognition Shortcuts
Medical Biochemical Genetics questions often present a clinical picture plus a laboratory finding and ask you to identify the disorder, the affected pathway, or the next step. These shortcuts help you sort the possibilities quickly.
- Hyperammonemia with respiratory alkalosis: think urea cycle first, then separate organic acidemias by the presence of metabolic acidosis and ketosis.
- Hypoketotic hypoglycemia: think fatty acid oxidation disorders before carbohydrate causes, then confirm with acylcarnitines.
- Elevated lactate with neurologic regression: think mitochondrial disease or pyruvate metabolism, and use the lactate-to-pyruvate relationship to refine.
- Coarse features with organomegaly: think mucopolysaccharidoses or oligosaccharidoses, then use urine glycosaminoglycan or oligosaccharide patterns.
- Neonatal seizures with dysmorphology and very long chain fatty acid elevation: think peroxisomal biogenesis disorders.
- Liver disease with neurologic or psychiatric features and low ceruloplasmin: think Wilson disease within the metals domain.
These are starting points, not diagnoses. The exam will present variations that test whether you can tolerate a partial pattern. Practicing varied vignettes on the MBG practice exam platform helps you learn which features are decisive and which are merely suggestive.
Scheduling Your Review by Domain Weight
The only study-planning idea worth repeating here is to allocate time in proportion to blueprint weight, then reserve a final pass for cross-domain connections. A sample sequence follows, using the blueprint percentages as the guide. For a fuller plan, see MBG Study Guide 2026: How to Pass on Your First Attempt.
Amino Acids and Cofactors
- Build pathway maps for phenylalanine, urea cycle, branched-chain, and homocysteine metabolism
- Pair each disorder with any cofactor-responsive variant, since cofactors link directly to this domain
Organic Acids and Mitochondria
- Practice reading organic acid patterns and naming the block
- Connect lactic acidosis and pyruvate findings to oxidative phosphorylation defects
Lipids, Carbohydrates, and Peroxisomes
- Organize fatty acid oxidation defects by chain length and acylcarnitine signature
- Review glycogen storage types by organ involvement and galactose/fructose triggers
Lysosomes and the Small Domains
- Sort storage disorders by substrate class
- Sweep purines/pyrimidines, transport, creatine, neurotransmitters, metals, and other
Laboratory and Integration
- Review assay platforms, newborn screening logic, and pre-analytic pitfalls
- Work mixed vignettes that cross domain boundaries
Adjust the order to your own background. A candidate with strong clinical metabolism experience may compress the first two weeks, while someone coming from a laboratory background may need more time on clinical presentation and management.
What Public Sources Do Not Verify
It is worth being direct about what this cheat sheet cannot include. The sources reviewed for this article, namely the ABMGG 2025 Biochemical Genetics Blueprint and Content Codes, list official exam content topics and approximate percentages. The public sources reviewed did not verify a public question count, a fee, a pass rate, or a testing provider for this specialty examination.
That means any page quoting a specific number of questions, a dollar figure, or a pass percentage as settled fact should be treated with caution unless it cites ABMGG directly. Confirm scheduling, registration steps, and costs with ABMGG itself before you commit. Our related pages discuss these topics qualitatively and in context: MBG Certification Cost 2026: Complete Pricing Breakdown, MBG Pass Rate 2026: What the Data Shows, MBG Passing Score 2026: Exactly What You Need to Pass, and MBG Exam Dates 2026: Testing Windows, Deadlines & Scheduling.
Is it worth the effort?
Whether the credential suits your career depends on your role, your institution, and your path in clinical or laboratory genetics. For a structured look at career value, read Is the MBG Certification Worth It? Complete ROI Analysis 2026, and for difficulty expectations see How Hard Is the MBG Exam? Complete Difficulty Guide 2026. Employment context is covered in MBG Jobs and MBG Salary Guide 2026: Complete Earnings Analysis.
Frequently Asked Questions
Here MBG means Medical Biochemical Genetics, the specialty examined through the American Board of Medical Genetics and Genomics (ABMGG). The same three letters are used by other credentials, so confirm that any resource you rely on is about Medical Biochemical Genetics specifically.
Amino acids is the largest at approximately 15%. Lipids follows at 13%, with organic acids and lysosomes each at 12%, and carbohydrates at 10%. The laboratory domain is 8%.
Treat them as approximate emphasis rather than exact counts. The blueprint gives official content topics and approximate percentages, and the public sources reviewed did not verify a public question count, so avoid assuming a fixed number per domain.
Yes, briefly. Creatine is about 1% and neurotransmitters about 2%, but the content is compact and learnable. Together the seven smallest domains cover roughly 18% of the blueprint, so skipping them entirely is a poor trade.
Go directly to ABMGG. The public sources reviewed for this article did not verify a fee, pass rate, or testing provider for this specialty examination, so official confirmation is the safe route. See our exam dates guide for how to approach scheduling questions.
Keep this sheet beside your notes, rebuild the domain table from memory a few days before test day, and use the MBG practice tests to find which clusters still need work. For a broader orientation to the credential, the MBG Cheat Sheet 2026: One-Page Review of Must-Know Facts remains the quickest recap of the essentials.