Gene: 🧾 A region of DNA that encodes a protein.
Genome: 🌍 The complete set of genes of an organism, including coding and non-coding DNA sequences.
Locus: 📍 The specific location of a gene on a chromosome.
Chromosome: 📦 Self-replicating structures containing DNA. Humans have 23 pairs (22 autosomes + 1 sex pair).
Alleles: 🔀 Alternative forms of a gene at the same locus; one allele inherited from each parent.
Haploid: 🎯 A single set of 23 chromosomes (e.g., egg or sperm).
Codon: 🧩 A 3-base sequence of nucleotides encoding a specific amino acid.
Karyotype: 🔬 The number and appearance of chromosomes in a nucleus (46 in humans = 44 autosomes + 2 sex chromosomes).
Autosome: 🚹🚺 Any chromosome other than the sex chromosomes (22 pairs in humans).

Inheritance Pearl: 🟢 Autosomal recessive → usually metabolic disorders (exceptions: inherited ataxias). 🔵 Autosomal dominant → usually structural disorders (exceptions: hyperlipidaemia type II, hypokalaemia periodic paralysis).

🟢 Autosomal Recessive Conditions (Metabolic)

Usually enzymatic or metabolic defects; both alleles must be faulty:

⚪ Albinism
⚪ Ataxia telangiectasia
⚪ Charcot-Marie-Tooth type 4
⚪ Hemochromatosis
⚪ Cystic fibrosis
⚪ Cystinosis
⚪ Fanconi anaemia
⚪ Familial Mediterranean fever
⚪ Homocystinuria
⚪ Sickle cell disease
⚪ Thalassemia
⚪ Phenylketonuria
⚪ Refsum’s disease
⚪ Lipid storage diseases (Tay-Sachs, Gaucher’s, Niemann-Pick)
⚪ Mucopolysaccharidoses (Hurler’s syndrome, etc.)
⚪ Retinitis pigmentosa (AR form)
⚪ Wilson’s disease

🔵 Autosomal Dominant Conditions (Structural)

Often affect connective tissue, receptors, or structural proteins:

🔹 Achondroplasia
🔹 Aniridia
🔹 Tuberous sclerosis
🔹 Charcot-Marie-Tooth types 1 & 2
🔹 Myotonic dystrophy
🔹 Gilbert’s syndrome
🔹 Hyperlipidemia type II
🔹 Ehlers-Danlos syndrome
🔹 Facioscapulohumeral muscular dystrophy
🔹 Familial hypercholesterolemia
🔹 Marfan syndrome
🔹 Multiple Endocrine Neoplasia (MEN)
🔹 Neurofibromatosis 1 & 2
🔹 Polycystic kidney disease (ADPKD)
🔹 Retinitis pigmentosa (AD form)
🔹 Retinoblastoma
🔹 Von Willebrand’s disease

🧑‍🍼 X-Linked Recessive Conditions

Affect males (only one X chromosome). Females usually carriers unless they have Turner syndrome (XO).

❌ G6PD deficiency
❌ Hunter syndrome
❌ Hemophilia A & B
❌ Fabry disease
❌ Duchenne & Becker muscular dystrophy
❌ Androgen insensitivity syndrome
❌ Color blindness
❌ Lesch-Nyhan syndrome
❌ Nephrogenic diabetes insipidus
❌ Ocular albinism
❌ Retinitis pigmentosa (X-linked)
❌ Severe combined immunodeficiency
❌ Wiskott-Aldrich syndrome

🧬 X-Linked Dominant Conditions

⭐ Vitamin D-resistant rickets (more severe in males)
⭐ Alport syndrome (85% X-linked dominant)
⭐ Rett syndrome

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Genetic Diseases

🧬 Genetic Definitions

🟢 Autosomal Recessive Conditions (Metabolic)

🔵 Autosomal Dominant Conditions (Structural)

🧑‍🍼 X-Linked Recessive Conditions

🧬 X-Linked Dominant Conditions

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