Question

1.Genetic and metabolic disorder. 2.Genetic and chromosomal disorder. 3.Single gene disorder

Answer 1

Do you want definitions, examples, or both? I’ll assume you want a concise definition plus common examples and key points for each category.

1) Genetic and metabolic disorder
- Definition: A genetic defect that disrupts a metabolic pathway (often enzyme deficiency), causing accumulation or deficiency of metabolites.
- Classic examples:
- Phenylketonuria (PKU) — PAH deficiency, autosomal recessive; high phenylalanine → intellectual disability if untreated; treat with low-Phe diet ± sapropterin.
- Maple syrup urine disease — branched-chain α-ketoacid dehydrogenase deficiency, autosomal recessive; branched-chain amino acids accumulate; treat with dietary restriction.
- Tay–Sachs disease and other lysosomal storage disorders (e.g., Gaucher) — enzyme defects → substrate buildup; variable inheritance (most autosomal recessive).
- Wilson disease — ATP7B mutation causing copper accumulation; autosomal recessive; treat with chelators/zinc.
- Diagnosis: newborn screening, metabolite assays, enzymology, targeted gene testing or panels.
- Note: Many single-gene disorders are metabolic in nature.

2) Genetic and chromosomal disorder
- Definition: Disorders caused by whole-chromosome number abnormalities or structural chromosome changes (deletions, duplications, translocations).
- Common examples:
- Down syndrome (trisomy 21) — intellectual disability, characteristic facies, congenital heart defects.
- Turner syndrome (45,X) — short stature, gonadal dysgenesis.
- Klinefelter syndrome (47,XXY) — hypogonadism, infertility.
- Cri-du-chat syndrome — 5p deletion with high-pitched cry, developmental delay.
- Diagnosis: karyotype, chromosomal microarray (CMA), sometimes FISH or prenatal screening.
- Inheritance: often de novo nondisjunction or deletion; some structural abnormalities may be inherited from a balanced carrier parent.

3) Single-gene (monogenic) disorder
- Definition: Disease caused by pathogenic variants in a single gene; inheritance follows Mendelian patterns (autosomal dominant, autosomal recessive, X-linked) or mitochondrial.
- Examples by inheritance:
- Autosomal recessive: Cystic fibrosis (CFTR), sickle cell disease (HBB).
- Autosomal dominant: Marfan syndrome (FBN1), familial hypercholesterolemia.
- X-linked: Duchenne muscular dystrophy (DMD), hemophilia A (factor VIII).
- Trinucleotide repeat expansion: Huntington disease (HTT) — autosomal dominant with anticipation.
- Diagnosis: targeted single-gene testing, multigene panels, exome/genome sequencing.
- Note: Single-gene disorders can be metabolic (e.g., PKU) or affect structural proteins, receptors, ion channels, etc.

If you want, I can:
- Give a short differential list for a specific clinical presentation,
- Provide inheritance/recurrence risk calculations for a family,
- Or supply diagnostic workflows (which test to order first) for each category. Which would be most useful?