Tt `xx` tt is

Options

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

Answer

### Step-by-Step Solution:

1. **Understanding the Genotypes**:
- The given genotypes are Tt (heterozygous) and tt (homozygous recessive).
- T represents the dominant allele, while t represents the recessive allele.

2. **Identifying the Cross**:
- The cross involves Tt (dominant phenotype) with tt (recessive phenotype).
- This type of cross is known as a **test cross** because it helps determine the genotype of the dominant phenotype by crossing it with a homozygous recessive individual.

3. **Setting Up the Punnett Square**:
- To visualize the potential offspring, we can set up a Punnett square.
- The alleles from Tt will be T and t, while the alleles from tt will both be t.

| | t | t |
|-----|-----|-----|
| T | Tt | Tt |
| t | tt | tt |

4. **Analyzing the Results**:
- From the Punnett square, we can see the possible genotypes of the offspring:
- 50% Tt (heterozygous, dominant phenotype)
- 50% tt (homozygous recessive, recessive phenotype)

5. **Conclusion**:
- The correct answer to the question is that the cross Tt x tt is a **test cross**. This method is used to determine the genotype of an organism with a dominant phenotype by crossing it with a homozygous recessive individual.