A cross used to ascertian whether an individual is dominant homozygous or heterozygous is termed :

Options

A. Reciprocal
B. Back cross
C. Test cross
D. Monohybrid

Answer

To determine whether an individual exhibiting a dominant phenotype is homozygous dominant or heterozygous, we can perform a specific type of genetic cross. Here’s a step-by-step explanation of the solution:

### Step-by-Step Solution:

1. **Understanding the Phenotype**: The individual in question shows a dominant phenotype (e.g., tall plants represented by 'T'). This individual could either be homozygous dominant (TT) or heterozygous (Tt).

2. **Choosing a Recessive Individual**: To ascertain the genotype of the dominant phenotype individual, we need to cross it with a recessive individual. The recessive individual will have the genotype (tt), which expresses the recessive phenotype (e.g., dwarf plants).

3. **Performing the Test Cross**: The cross between the dominant phenotype individual (which we are testing) and the recessive individual is called a **test cross**. This is a standard method used in genetics to determine the genotype of an organism with a dominant phenotype.

4. **Analyzing the Offspring**:
- If all offspring from this cross exhibit the dominant phenotype (tall), it indicates that the tested individual is homozygous dominant (TT).
- If the offspring show a 1:1 ratio of dominant (tall) to recessive (dwarf) phenotypes, it indicates that the tested individual is heterozygous (Tt).

5. **Conclusion**: Therefore, the correct term for the cross used to ascertain whether an individual is homozygous dominant or heterozygous is a **test cross**.

### Final Answer:
The cross used to ascertain whether an individual is dominant homozygous or heterozygous is termed a **test cross**.

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