Degree of Phenotypic Expression
The degree or extent to which a given genotype is expressed phenotypically is known as-
- Epistasis
- Expressivity — Correct Answer
- Penetrance
- Recessive
Explanation:
Correct Answer: Expressivity
Expressivity refers to the degree or extent to which a given genotype is expressed phenotypically. It describes how strongly a trait manifests, not whether it manifests at all.
Expressivity — Key Facts
- Definition: Variation in intensity or severity of the phenotype among individuals sharing the same genotype
- Example: In neurofibromatosis, some individuals show a few spots while others show many — same genotype, different expressivity
- Influenced by: Modifier genes, environmental factors, genetic background
Penetrance vs. Expressivity — Comparison
| Feature | Penetrance | Expressivity |
|---|---|---|
| Definition | % of individuals showing the expected phenotype | Degree/extent of phenotypic expression |
| Measurement | Qualitative (yes/no) | Quantitative (how much) |
| Example | 100% penetrance = all carriers express trait | Variable expressivity = different severities |
Why Other Options Are Wrong
- Epistasis → masking effect of one gene over another; not about degree of expression
- Penetrance → percentage of individuals with a given genotype that express the phenotype (not the degree)
- Recessive → type of allele relationship; unrelated to degree of expression
📚 About this Topic — Animal Genetics & Breeding
This multiple choice question is from Animal Genetics & Breeding, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Genetics & Breeding to strengthen your preparation.
