In polygenic inheritance

Options

A. many genes govern a single character
B. heterozygous organisms express only one allele itself
C. heterozygous organisms express both alleles
D. a single gene influences many characters

Answer

**Step-by-Step Solution:**

1. **Understanding Polygenic Inheritance**: Polygenic inheritance refers to the phenomenon where multiple genes (polygenes) contribute to a single trait. This means that a single characteristic is influenced by more than one gene, each having a small additive effect on the phenotype.

2. **Analyzing the Options**:
- **Option A**: "Many genes govern a single character." This statement is true and aligns with the definition of polygenic inheritance.
- **Option B**: "Heterozygous organisms express only one allele itself." This is incorrect as heterozygous organisms express both alleles.
- **Option C**: "Heterozygous organisms express both alleles." This is true, but it does not pertain specifically to polygenic inheritance.
- **Option D**: "A single gene influences many characters." This is a description of pleiotropy, not polygenic inheritance.

3. **Conclusion**: The correct answer is **Option A**: "Many genes govern a single character."

4. **Examples of Polygenic Inheritance**: Common examples of polygenic traits in humans include skin color, hair color, height, and eye color. Each of these traits is influenced by multiple genes, making them quantitative traits.

5. **Differentiating from Other Concepts**: It is important to differentiate polygenic inheritance from multiple alleles and pleiotropy. In polygenic inheritance, multiple genes contribute to a single trait, while in multiple alleles, more than two alleles exist for a single gene locus, and in pleiotropy, one gene affects multiple traits.