In complete dominance

Options

A. Dominant trait is completely expressed in the generation
B. Phenotypic and genotypic ratio are different
C. Two dominant alleles are needed to express complete dominant trait
D. `F1` individuals have the equal traits of both parents

Answer

### Step-by-Step Solution:

1. **Understanding Complete Dominance**:
- Complete dominance occurs when the dominant allele completely masks the effect of the recessive allele in a heterozygous condition. This means that in the presence of a dominant allele, the recessive allele does not contribute to the phenotype.

2. **Analyzing the Statements**:
- We have four statements regarding complete dominance that we need to evaluate as true or false.

3. **Evaluating Statement 1**:
- **Statement**: "Dominant trait is completely expressed in the generation."
- **Evaluation**: This statement is **True**. In the F1 generation, if we cross a red flower (RR) with a white flower (rr), all offspring (Rr) will express the dominant trait, which is red color.

4. **Evaluating Statement 2**:
- **Statement**: "Phenotypic and genotypic ratio are different."
- **Evaluation**: This statement is **False**. In the F1 generation, all offspring have the same genotype (Rr) and the same phenotype (red color), leading to a phenotypic and genotypic ratio of 1:1.

5. **Evaluating Statement 3**:
- **Statement**: "Two dominant alleles are needed to express complete dominant trait."
- **Evaluation**: This statement is **False**. A single dominant allele (R) is sufficient to express the dominant trait, even in a heterozygous condition (Rr).

6. **Evaluating Statement 4**:
- **Statement**: "F1 individuals have the equal traits of both parents."
- **Evaluation**: This statement is **False**. The F1 individuals only exhibit the trait of the dominant parent (red color) and do not show the trait of the recessive parent (white color).

7. **Conclusion**:
- After evaluating all statements, only the first statement is true. Therefore, the correct answer is that **only the first statement is true**.

### Final Answer:
- The only true statement regarding complete dominance is: "Dominant trait is completely expressed in the generation."

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