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 genotypes with dominant trait

Answer

To solve the question "Test cross involves-", we will break down the concept of a test cross step by step.

### Step-by-Step Solution:

1. **Understanding Test Cross**:
- A test cross is a genetic cross used to determine the genotype of an organism exhibiting a dominant phenotype. It helps to identify whether the organism is homozygous (having two identical alleles) or heterozygous (having two different alleles) for a particular trait.

**Hint**: Remember that a test cross is specifically designed to reveal the genetic makeup of an organism with a dominant trait.

2. **Components of a Test Cross**:
- In a test cross, we typically take an F1 hybrid organism (which is heterozygous) and cross it with a homozygous recessive organism. The recessive organism is usually represented by two lowercase letters (e.g., "tt" for a trait).

**Hint**: The recessive parent must be homozygous to ensure that any dominant traits from the F1 hybrid can be clearly observed in the offspring.

3. **Example of a Test Cross**:
- For instance, if we have a plant that is heterozygous for a trait (Tt, where "T" is dominant and "t" is recessive), we would cross it with a homozygous recessive plant (tt).

**Hint**: Use the letters "T" and "t" to visualize how the dominant and recessive traits will segregate in the offspring.

4. **Results of a Test Cross**:
- The offspring from this cross can be either dominant (Tt) or recessive (tt). The ratio of the offspring will help determine the genotype of the F1 hybrid. If all offspring show the dominant trait, the F1 is homozygous (TT). If there is a mix, the F1 is heterozygous (Tt).

**Hint**: Pay attention to the offspring ratios; they provide crucial information about the parent's genotypes.

5. **Choosing the Correct Option**:
- Given the options provided in the question, the correct answer is: "crossing the F1 hybrid with a double recessive genotype parent." This accurately describes the process of a test cross.

**Hint**: Always look for the option that specifies crossing a hybrid with a recessive parent to identify the genotype.

### Final Answer:
Test cross involves crossing an F1 hybrid with a double recessive genotype parent.