Genetic Principles and Inheritance Patterns

Genetic Principles and Patterns of Inheritance

• Human Genetics Overview
  • Focuses on genetic principles, diversity, and applications.

Key Themes in Genetics Lectures

• Structure and Function
  • Genome, chromosomes, DNA, and packaging
  • Genes: roles in transcription and translation
• Replication
  • Mitosis and mutations
• Reproduction
  • Meiosis, recombination, chromosome number variations
• Laws of Inheritance
  • Discusses monogenic disorders and pedigrees
• Genetic Variation
  • Reflects evolutionary history and global genetic diversity
• Genes and Society
  • Applications in personalized medicine.

Inheritance Patterns

• Monogenic Disorders
  • Simple autosomal dominant or recessive traits
  • Examples: Phenylketonuria (PKU), Alkaptonuria, Albinism
• Complex Disorders
  • Involve multiple genes and environmental factors
  • Examples: Type 2 diabetes, primary immunodeficiencies.

Fundamental Genetic Principles

1. Pleiotropy:

   • A single gene influences multiple traits.
   • E.g., one gene affects both pigmentation and cognitive function.

2. Variable Expression:

   • Different individuals may express the same gene differently due to genetic or environmental factors.
   • Associated with different mutations, often missense mutations in genes.

3. Genotype-Environment Interaction:

   • The expression of diseases can be influenced by environmental conditions.
   • Example: PKU causes symptoms only with a high phenylalanine diet.

4. Genetic Heterogeneity:

   • One phenotype may be caused by mutations in several different genes.
   • E.g., several genes can result in conditions like albinism.

Inborn Errors of Metabolism

• Characterized by enzyme deficiencies
  • Usually inherited recessively
  • Symptoms arise from substrate accumulation, product deficiency, or pathway disturbances
  • Examples include PKU, Alkaptonuria, and Albinism.

Phenylketonuria (PKU) Overview

• Symptoms:
  • Cognitive impairment and heightened blood phenylalanine levels
  • Light pigmentation (fair hair and skin).
• Prevalence:
  • Varies among populations; approximately 1 in 10,000 births, caused by autosomal recessive mutations.
• Management:
  • Dietary restrictions on phenylalanine and early screening post-birth.

Genetic Testing and GWAS

• GWAS (Genome-Wide Association Studies):
  • Used to identify genetic variants associated with diseases by comparing variant frequencies between affected and control cohorts.
  • Important for understanding complex traits, e.g., the correlation between genetic variants and treatment responses in diseases like hepatitis C.

Summary of Important Genetic Concepts

• Genes and their effects can vary widely across individuals and populations.

• The interplay of genetic and environmental factors is critical in the manifestation of both monogenic and complex traits.

• Recognizing these principles is essential for advancing personalized medicine and understanding disease mechanisms.