NEET PG High-Yield: Genotype vs. Phenotype
Understanding the distinction between an organism’s genetic makeup and its observable traits is fundamental to medical genetics.
Core Definitions
- Genotype: The complete genetic constitution of an individual (the specific alleles present at a locus).
- Phenotype: The observable physical, biochemical, or physiological characteristics of an individual, determined by the interaction of genotype and environment.
Phenotype = Genotype + Environment
Key Concepts
| Concept | Description |
|---|---|
| Penetrance | The proportion of individuals with a genotype who show the associated phenotype. |
| Expressivity | The degree or severity to which a given genotype is expressed in an individual. |
| Phenocopy | An environmentally induced trait that mimics a genetic condition (e.g., thalidomide-induced limb defects mimicking genetic syndromes). |
High-Yield NEET PG Pearls:
- Environment influence: Many diseases (e.g., Diabetes, Hypertension) are multifactorial, where phenotype depends heavily on diet/lifestyle interacting with genotype.
- Dominance: A dominant allele dictates the phenotype even in the heterozygous state.
- Recessiveness: The recessive phenotype is only expressed in the homozygous state.