A pure tall and a pure dwarf plant were crossed to produce offsprings. Offsprings were self crossed, then find out the ratio between true breeding tall to true breeding dwarf?

Options

A. `1:1`
B. `3:1`
C. `2:1`
D. `1:2:1`

Answer

To solve the problem of determining the ratio between true breeding tall and true breeding dwarf plants after crossing a pure tall plant with a pure dwarf plant and then self-crossing the offspring, we can follow these steps:

### Step 1: Understand the Parental Generation
We start with two pure plants:
- Pure tall plant (TT)
- Pure dwarf plant (tt)

### Step 2: Cross the Parental Generation
When we cross these two plants, we can determine the genotype of the offspring:
- The gametes from the tall plant (TT) can only be T.
- The gametes from the dwarf plant (tt) can only be t.

When we cross them:
- Offspring genotype: Tt (all offspring will be heterozygous tall)

### Step 3: Self-Cross the Offspring
Now, we self-cross the offspring (Tt x Tt):
- The possible gametes from each Tt plant are T and t.

### Step 4: Create a Punnett Square
We can set up a Punnett Square to visualize the self-cross:

| | T | t |
|-------|-------|-------|
| **T** | TT | Tt |
| **t** | Tt | tt |

### Step 5: Analyze the Offspring Genotypes
From the Punnett Square, we can see the following genotypes:
- TT (true breeding tall) = 1
- Tt (tall but not true breeding) = 2
- tt (true breeding dwarf) = 1

### Step 6: Determine the Ratio
Now, we can summarize the counts:
- True breeding tall (TT) = 1
- True breeding dwarf (tt) = 1

Thus, the ratio of true breeding tall to true breeding dwarf is:
- **1:1**

### Final Answer
The ratio between true breeding tall to true breeding dwarf is **1:1**.

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