When two hybrids Ttrr & Rrtt are crossed, the phenotypic ratio of offspring shall be .

Options

A. `3 : 1`
B. `1 : 1 : 1 :1`
C. `1 : 1`
D. `9 : 3 : 3 : 1`

Answer

To solve the problem of determining the phenotypic ratio of the offspring when two hybrids Ttrr (Tall, wrinkled) and Rrtt (Dwarf, round) are crossed, we can follow these steps:

### Step 1: Identify the Genotypes of the Parents
The two hybrids are:
- Parent 1: Ttrr (Tall, wrinkled)
- Parent 2: Rrtt (Dwarf, round)

### Step 2: Determine the Gametes Produced by Each Parent
Each parent can produce different types of gametes based on their alleles:
- Parent 1 (Ttrr) can produce gametes: Tr, tr
- Parent 2 (Rrtt) can produce gametes: Rt, rt

### Step 3: Set Up a Punnett Square
Now, we can set up a Punnett square to visualize the combinations of these gametes.

```
Rt rt
----------------
Tr | TrRt | Trrt |
----------------
tr | trRt | trrt |
----------------
```

### Step 4: Determine the Genotypes of the Offspring
From the Punnett square, we can identify the genotypes of the offspring:
1. TrRt (Tall, round)
2. Trrt (Tall, wrinkled)
3. trRt (Dwarf, round)
4. trrt (Dwarf, wrinkled)

### Step 5: Identify the Phenotypes
Now, we can determine the phenotypes based on the dominant and recessive traits:
- Tall (T) is dominant over Dwarf (t)
- Round (R) is dominant over Wrinkled (r)

Thus, the phenotypes corresponding to the genotypes are:
1. TrRt - Tall, Round
2. Trrt - Tall, Wrinkled
3. trRt - Dwarf, Round
4. trrt - Dwarf, Wrinkled

### Step 6: Count the Phenotypes
Now we can count the number of each phenotype:
- Tall, Round: 1
- Tall, Wrinkled: 1
- Dwarf, Round: 1
- Dwarf, Wrinkled: 1

### Step 7: Calculate the Phenotypic Ratio
The phenotypic ratio of the offspring is:
- Tall, Round : Tall, Wrinkled : Dwarf, Round : Dwarf, Wrinkled = 1:1:1:1

### Final Answer
The phenotypic ratio of the offspring when Ttrr is crossed with Rrtt is **1:1:1:1**.

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