Test cross involves

Options

A. Crossing between two genotypes with recessive trait
B. Crossing between two `F_(1)` hybrids
C. Crossing the `F_(1)` hybrid with a double recessive genotype
D. Crossing between two genotype with dorminant trait

Answer

**Step-by-Step Solution:**

1. **Understanding Test Cross**: A test cross is a genetic cross used to determine the genotype of an organism showing a dominant phenotype. This is done by crossing the organism with a homozygous recessive individual.

2. **Identifying the Genotypes**: In the case of a trait like plant height, we have two alleles: one for tallness (dominant, represented as 'T') and one for dwarfness (recessive, represented as 't'). The tall plant can either be homozygous dominant (TT) or heterozygous (Tt).

3. **Performing the Test Cross**: To determine whether the tall plant is homozygous (TT) or heterozygous (Tt), we perform a test cross with a homozygous recessive plant (tt).

4. **Analyzing the Offspring**:
- If all offspring from the test cross are tall, then the tall parent must be homozygous dominant (TT).
- If the offspring are a mix of tall and dwarf plants (50% tall and 50% dwarf), then the tall parent must be heterozygous (Tt).

5. **Conclusion**: The test cross helps in determining the genotype of the tall plant based on the phenotypes of the offspring produced.

**Final Answer**: The correct answer to the question "Test cross involves" is: **Crossing the F1 hybrid with a homozygous recessive genotype.**

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