Number of genotype found in `F_(2)` progeny of a dihybrid cross is

Options

A. 9
B. 6
C. 3
D. 1

Answer

To determine the number of genotypes found in the F2 progeny of a dihybrid cross, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Dihybrid Cross**: A dihybrid cross involves two traits, each represented by two alleles. For example, let’s consider the traits for plant height (Tall - T, Dwarf - t) and seed shape (Round - R, Wrinkled - r).

2. **Identify Parental Genotypes**: The parental generation (P) will consist of one plant that is homozygous tall and round (TTRR) and another that is homozygous dwarf and wrinkled (ttrr).

3. **F1 Generation**: When these two plants are crossed, all offspring in the F1 generation will be heterozygous for both traits (TtRr). This means all F1 plants will exhibit the dominant phenotypes (Tall and Round).

4. **Self-Pollination of F1**: To obtain the F2 generation, we self-pollinate the F1 plants (TtRr x TtRr).

5. **Use of Punnett Square**: We can use a Punnett square to determine the genotypes of the F2 progeny. Since we are dealing with two traits, we will create a 4x4 Punnett square.

6. **Count the Genotypes**: From the Punnett square, we can identify the different genotypes:
- **TTRR** (Tall, Round)
- **TTRr** (Tall, Round)
- **TtRR** (Tall, Round)
- **TtRr** (Tall, Round)
- **TtRr** (Tall, Round)
- **Ttrr** (Tall, Wrinkled)
- **ttRR** (Dwarf, Round)
- **ttRr** (Dwarf, Round)
- **ttrr** (Dwarf, Wrinkled)

7. **Total Unique Genotypes**: After listing all the combinations, we find that there are 9 unique genotypes in total:
- 1 TT R R
- 2 T T r r
- 2 T t R R
- 4 T t R r
- 2 t t R R
- 2 t t R r
- 1 t t r r

Thus, the total number of genotypes in the F2 generation of a dihybrid cross is **9**.

### Final Answer:
The number of genotypes found in the F2 progeny of a dihybrid cross is **9**.