What will be the total number of phenotypes and genotypes obtained in F2 generation of a dihybrid test cross ?

Options

A. 5
B. 3
C. 8
D. 6

Answer

To determine the total number of phenotypes and genotypes obtained in the F2 generation of a dihybrid test cross, we can follow these steps:

### Step 1: Understand the Dihybrid Cross
In a dihybrid cross, we are dealing with two traits. For example, let's consider the traits of seed shape (round vs. wrinkled) and seed color (yellow vs. green). The dominant traits are round (R) and yellow (Y), while the recessive traits are wrinkled (r) and green (y).

### Step 2: Identify the Genotypes of Parents
In a test cross, we cross a heterozygous individual with a homozygous recessive individual. For our example:
- The heterozygous parent (F1 generation) would be RrYy (round and yellow).
- The homozygous recessive parent would be rryy (wrinkled and green).

### Step 3: Determine Gametes
The heterozygous parent (RrYy) can produce four types of gametes:
- RY
- Ry
- rY
- ry

The homozygous recessive parent (rryy) can only produce one type of gamete:
- ry

### Step 4: Create a Punnett Square
Now, we can set up a Punnett square to determine the genotypes of the offspring:
```
ry
-------------
| RY | Ry | rY | ry |
-------------------------
```
The combinations from the Punnett square will be:
1. RrYy (Round and Yellow)
2. Rryy (Round and Green)
3. rrYy (Wrinkled and Yellow)
4. rryy (Wrinkled and Green)

### Step 5: Count Genotypes and Phenotypes
From the combinations, we can identify:
- **Genotypes**:
1. RrYy
2. Rryy
3. rrYy
4. rryy

This gives us a total of **4 different genotypes**.

- **Phenotypes**:
1. Round and Yellow (RrYy)
2. Round and Green (Rryy)
3. Wrinkled and Yellow (rrYy)
4. Wrinkled and Green (rryy)

This gives us a total of **4 different phenotypes**.

### Final Answer
Therefore, in the F2 generation of a dihybrid test cross, we will obtain a total of **4 genotypes and 4 phenotypes**.

### Summary
- Total Genotypes: 4
- Total Phenotypes: 4