Makindo Medical Notes

Related Subjects: |Autosomal Recessive |X Linked Recessive |Autosomal Dominant |Li Fraumeni syndrome |Genetic Linkage |Cell Cycle |DNA replication

Overview of Autosomal Dominant Inheritance

Autosomal dominant inheritance is a pattern of inheritance in which only one copy of a defective gene (inherited from one parent) is sufficient to cause the expression of a trait or disorder. This type of inheritance can result in various genetic disorders that may manifest in every generation.

Key Characteristics

• Affected Individuals :
  • Only one mutated copy of the gene is necessary for an individual to be affected.
  • Affected individuals have a 50% chance of passing the mutated gene to their offspring.
  • The disorder can be seen in every generation.
• Equal Gender Distribution :
  • Autosomal dominant disorders affect males and females equally.
• Variable Expressivity :
  • The severity of symptoms can vary among individuals with the same genetic mutation.
• Reduced Penetrance :
  • Some individuals with the mutated gene may not show symptoms of the disorder.

Examples of Autosomal Dominant Disorders

• Huntington's Disease :
  • Caused by mutations in the HTT gene.
  • Leads to progressive neurodegeneration and movement, cognitive, and psychiatric disorders.
• Marfan Syndrome :
  • Caused by mutations in the FBN1 gene.
  • Affects connective tissue, leading to cardiovascular, skeletal, and ocular abnormalities.
• Achondroplasia :
  • Caused by mutations in the FGFR3 gene.
  • Results in short stature and disproportionately short limbs.
• Familial Hypercholesterolemia :
  • Caused by mutations in the LDLR gene.
  • Leads to high cholesterol levels and an increased risk of cardiovascular disease.

Genetic Counseling and Testing

• Predictive Testing :
  • Genetic testing can identify individuals at risk for autosomal dominant disorders before symptoms appear.
• Prenatal Testing :
  • Can diagnose certain genetic disorders before birth through techniques like amniocentesis or chorionic villus sampling (CVS).
• Preimplantation Genetic Diagnosis (PGD) :
  • Used in conjunction with in vitro fertilization (IVF) to select embryos without the genetic disorder.
• Genetic Counseling :
  • Provides information and support to individuals and families affected by or at risk of genetic disorders.
  • Helps in understanding the risks, implications, and options available.

Management and Treatment

• Symptomatic Treatment :
  • Focuses on managing symptoms and improving quality of life.
  • Examples include physical therapy for Marfan syndrome and medications for Huntington's disease.
• Surgical Interventions :
  • May be necessary for conditions like Marfan syndrome to address cardiovascular issues.
• Lifestyle Modifications :
  • Diet and exercise modifications for managing familial hypercholesterolemia.
• Gene Therapy :
  • Emerging treatments aim to correct the underlying genetic defect.

Summary

Autosomal dominant inheritance requires only one copy of a mutated gene for a disorder to be expressed. Understanding the key characteristics, examples of disorders, genetic counseling, and treatment options is crucial for managing and supporting individuals and families affected by these genetic conditions.