Phenotype Reflects the Observable Traits of an Organism
Definition
Phenotype
The phenotype of an organism refers to its observable traits or characteristics, which result from the interaction between its genetic makeup (genotype) and the environment.
- These traits can be structural (e.g., eye color), functional (e.g., blood clotting speed), or behavioral (e.g., language spoken).
- While some traits are purely genetic, many result from the dynamic interaction between genes and the environment.
Traits determined solely by genotype are often used in forensic science because they remain unchanged throughout an individual's life.
Traits Categorized by Their Determining Factors
Phenotypic traits can be classified based on whether they are determined solely by genotype, solely by the environment, or by a combination of both.
| Genotype Only | Environment and Genotype | Environment Only |
|---|---|---|
| Eye color—brown or blue/grey | Height in humans | Scars from surgery or wounds |
| ABO blood group | Skin color (affected by sun exposure) | River blindness (caused by environmental parasites) |
| Haemophilia—blood slow to clot | Diabetes (affected by lifestyle and genetics) | Language or accent |
Genotype and Environment
- The majority of traits arise from the interaction of genotype and environment:
- Height: Genes set the potential range for height, but environmental factors like nutrition during childhood determine the final outcome.
- Skin color: Genetic factors control baseline melanin production, but exposure to sunlight triggers tanning, altering visible skin tone.
- Diabetes: Influenced by both genetic predisposition and lifestyle factors.
- How does the concept of phenotype challenge the idea of nature versus nurture?
- Are there traits where one clearly dominates, or is it always a combination?
- Define phenotype and explain how it differs from genotype.
- Give two examples of human traits determined by genotype only, two examples determined by environment only, and two examples determined by both genotype and environment.
- Explain why height in humans is considered a trait influenced by both genotype and environment. What role does each factor play?
