A test cross can be conducted to differentiate between a homozygous and a heterozygous

Options

A. dominant genotype
B. dominant phenotype
C. recessive genotype
D. recessive phenotype

Answer

### Step-by-Step Solution

1. **Understanding the Concept of Test Cross**:
A test cross is a genetic cross performed to determine whether an individual exhibiting a dominant phenotype is homozygous (pure) or heterozygous (hybrid) for a particular trait.

2. **Identifying the Parents for the Test Cross**:
The individual with the dominant phenotype (which can be either homozygous dominant or heterozygous) is crossed with a homozygous recessive individual. The recessive individual will express the recessive phenotype, which helps in determining the genotype of the dominant individual.

3. **Example of the Test Cross**:
Consider a plant that is tall (dominant trait) and we want to determine if it is homozygous tall (TT) or heterozygous tall (Tt). We can cross this tall plant with a dwarf plant (homozygous recessive, tt).

4. **Analyzing the Offspring**:
- If the tall plant is homozygous (TT), all offspring from the cross will be tall (Tt).
- If the tall plant is heterozygous (Tt), the offspring will be in a 1:1 ratio: half will be tall (Tt) and half will be dwarf (tt).

5. **Interpreting the Results**:
- If all offspring are tall, the original tall plant is homozygous (TT).
- If there is a mix of tall and dwarf offspring, the original tall plant is heterozygous (Tt).

6. **Conclusion**:
A test cross is an effective method to differentiate between homozygous and heterozygous individuals for a dominant trait by examining the phenotypes of the offspring produced from the cross.