Etiology of Diseases: Most diseases are due to a complex interaction between environmental factors (external or internal) and genetic material.
Nature vs. Nurture Debate: It's not about one influencing more than the other; rather, it's an interaction between nature (genetics) and nurture (environment).
Focus on Genetics: The lecture emphasizes understanding the genetic component of diseases.
DNA and Chromosomes
DNA: Deoxyribonucleic acid, located in the nucleus of cells (except red blood cells).
Chromosomes: DNA is compactly packed into 23 pairs of chromosomes in the nucleus.
Autosomes: Chromosomes 1-22 are autosomes.
Sex Chromosomes: The 23rd pair determines genetic sex (XX for females, XY for males).
Genetic material is inherited from parents, one chromosome per pair from each parent.
Genetic Inheritance
Autosomal Inheritance
Autosomal Recessive: Requires two dysfunctional copies of a gene from both parents to present with a disease.
Autosomal Dominant: Only one dysfunctional copy is needed to present with a disease.
Example: Huntington's disease (characterized by excessive CAG repeats in the Huntington gene).
Genes and Mutations
DNA Structure: Made up of base pairs (Adenine, Cytosine, Guanine, Thymine).
Genes: Segments of DNA that encode for proteins necessary for cell function.
Mutations
Loss of Function: Mutation results in non-functional protein, can lead to autosomal recessive diseases.
Gain of Function: Mutation enhances or changes protein function, leading to autosomal dominant diseases.
Sex-Linked Inheritance
X-Linked
Males (XY) more often present with X-linked diseases as they have a single X chromosome.
Females (XX): Can be carriers if one X chromosome is mutated.
Inheritance Patterns
If a father has an X-linked mutation, all daughters become carriers, sons are unaffected (inherit Y from father).
If a mother has a mutation, 50% of sons may present the disease, 50% of daughters may be carriers.
Conclusion
The lecture provides an oversimplified explanation of the genetic basis of disease and inheritance, focusing on the interaction between genetics and environment, and illustrating different inheritance patterns and their implications for disease.