The genotype of a dominant phenotype

Options

A. Only homozygous
B. Only heterozygous
C. Either homozygous or heterozygous
D. Neither homozygous nor heterzygous

Answer

To determine the genotype of a dominant phenotype, we need to understand the concepts of homozygous and heterozygous genotypes.

### Step-by-Step Solution:

1. **Define Homozygous**:
- A homozygous genotype means that an individual has two identical alleles for a particular gene. For example, if the dominant allele is represented as "A", a homozygous dominant genotype would be "AA".

2. **Define Heterozygous**:
- A heterozygous genotype means that an individual has two different alleles for a particular gene. For instance, if one allele is dominant (A) and the other is recessive (a), the heterozygous genotype would be "Aa".

3. **Understand Dominant Phenotype**:
- A dominant phenotype is expressed when at least one dominant allele is present. This means that both homozygous dominant (AA) and heterozygous (Aa) individuals will display the dominant trait.

4. **Analyze the Options**:
- Option A: Homozygous - This is correct for dominant phenotype (AA).
- Option B: Only heterozygous - This is incorrect as homozygous dominant also expresses the dominant phenotype.
- Option C: Either homozygous or heterozygous - This is correct as both can express the dominant phenotype.
- Option D: Neither homozygous nor heterozygous - This is incorrect as both genotypes can express the dominant phenotype.

5. **Conclusion**:
- Since both homozygous (AA) and heterozygous (Aa) genotypes can express a dominant phenotype, the correct answer is **Option C: either homozygous or heterozygous**.