How many phenotypic classes are produced for a pair of characters in a monohybrid test test cross

Options

A. 2
B. 4
C. 1
D. 3

Answer

To solve the question of how many phenotypic classes are produced for a pair of characters in a monohybrid test cross, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Test Cross**: A test cross is performed between an F1 hybrid (which is heterozygous) and a homozygous recessive parent. This helps determine the genotype of the F1 hybrid.

2. **Identify the Characters**: In a monohybrid test cross, we are dealing with a single contrasting pair of characters. For example, let's consider plant height where:
- Dominant trait (Tall) = represented by allele "T"
- Recessive trait (Dwarf) = represented by allele "t"

3. **Determine the F1 Generation**: The F1 generation from a cross between the homozygous tall (TT) and homozygous dwarf (tt) will be:
- F1 hybrid = Tt (all offspring will be tall because T is dominant)

4. **Perform the Test Cross**: The F1 hybrid (Tt) is crossed with the homozygous recessive parent (tt):
- Gametes from F1 hybrid (Tt): T and t
- Gametes from recessive parent (tt): t

5. **Possible Offspring**: The combinations of gametes will yield the following progeny:
- Tt (Tall)
- tt (Dwarf)

6. **Count the Phenotypic Classes**: The phenotypic classes produced from this cross are:
- Tall (Tt)
- Dwarf (tt)

7. **Conclusion**: Therefore, there are 2 phenotypic classes produced in a monohybrid test cross.

### Final Answer:
The number of phenotypic classes produced for a pair of characters in a monohybrid test cross is **2**.

---