Which Mendelian cross can produce two genotypes and two pheotypes ?

Options

A. Monohybrid cross
B. Monohybrid test cross
C. Incomplete dominance
D. Co-dominance

Answer

To determine which Mendelian cross can produce two genotypes and two phenotypes, we can analyze the options provided:

### Step-by-Step Solution:

1. **Understanding the Types of Crosses**:
- **Monohybrid Cross**: This involves a cross between two individuals that differ in one trait. It typically results in a 3:1 phenotypic ratio in the F2 generation.
- **Monohybrid Test Cross**: This is a cross between a heterozygous individual (e.g., Tt) and a homozygous recessive individual (e.g., tt). This cross helps determine the genotype of the heterozygous individual.
- **Incomplete Dominance**: In this type of inheritance, the phenotype of the heterozygote is intermediate between the phenotypes of the homozygotes. This can produce three phenotypes.
- **Co-dominance**: In co-dominance, both alleles in the heterozygote are fully expressed, leading to a distinct phenotype. This also results in three distinct phenotypes.

2. **Analyzing the Monohybrid Test Cross**:
- In a monohybrid test cross, if we take a heterozygous tall plant (Tt) and cross it with a homozygous recessive plant (tt), we can determine the genotypes of the offspring.
- The possible gametes from the heterozygous parent (Tt) are T and t, while the homozygous recessive parent (tt) can only produce t gametes.

3. **Resulting Offspring**:
- The resulting offspring from this cross would be:
- Tt (tall) from T and t
- tt (dwarf) from t and t
- This results in two genotypes: Tt and tt.
- The phenotypes observed would be tall (Tt) and dwarf (tt), leading to two distinct phenotypes.

4. **Conclusion**:
- Therefore, the Mendelian cross that can produce two genotypes and two phenotypes is the **Monohybrid Test Cross**.

### Final Answer:
The answer to the question is **B. Monohybrid Test Cross**.