What is the genotype of plants showing a dominant phenotype of violet flowers if it os test crossed and produced only violet flowered plants?

Options

A. VV
B. Vv
C. vv
D. v

Answer

To determine the genotype of plants showing a dominant phenotype of violet flowers that, when test crossed, produced only violet flowered plants, we can follow these steps:

### Step 1: Understand the Phenotype and Genotype
- The plants exhibit a dominant phenotype (violet flowers). In genetics, dominant traits are typically represented by a capital letter (e.g., "V" for violet flowers), while recessive traits are represented by lowercase letters (e.g., "v" for non-violet flowers).

### Step 2: Define the Test Cross
- A test cross is performed to determine the genotype of an organism expressing a dominant phenotype. This is done by crossing the organism with a homozygous recessive individual (in this case, "vv").

### Step 3: Analyze the Test Cross Results
- If the test cross produces only violet flowered plants, it indicates that all offspring exhibit the dominant phenotype. This means that the dominant allele must be present in both alleles of the parent plant.

### Step 4: Determine the Possible Genotypes
- The possible genotypes for the plant showing the dominant phenotype are:
- Homozygous dominant (VV)
- Heterozygous (Vv)

### Step 5: Conclude the Genotype
- Since the test cross resulted in only violet flowered plants, this rules out the heterozygous condition (Vv), as a heterozygous cross with a homozygous recessive (vv) would produce some offspring with the recessive phenotype (non-violet flowers). Therefore, the only possible genotype for the plant is homozygous dominant (VV).

### Final Answer
- The genotype of the plants showing a dominant phenotype of violet flowers is **homozygous dominant (VV)**.

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