The ratio of homozygous and hetrozygous organisms in the `F_(2)` of monohybrid corss

Options

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

Answer

To solve the question regarding the ratio of homozygous and heterozygous organisms in the F2 generation of a monohybrid cross, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Monohybrid Cross**:
In a monohybrid cross, we consider a single trait that is governed by two alleles (e.g., tall (T) and dwarf (t)). The parents are typically homozygous for the traits being studied.

2. **F1 Generation**:
When two homozygous parents (TT and tt) are crossed, all offspring in the F1 generation will be heterozygous (Tt). This means that they will all express the dominant trait (tall).

3. **F2 Generation**:
The F1 generation (Tt) is then allowed to self-pollinate or self-fertilize. The genotypes of the offspring in the F2 generation can be determined using a Punnett square.

4. **Constructing the Punnett Square**:
- The alleles from one parent (Tt) are placed on the top and the alleles from the other parent (Tt) are placed on the side.
- The resulting combinations will be:
- TT (homozygous dominant)
- Tt (heterozygous)
- Tt (heterozygous)
- tt (homozygous recessive)

5. **Counting the Genotypes**:
From the Punnett square, we can see the following genotypes:
- 1 TT (homozygous dominant)
- 2 Tt (heterozygous)
- 1 tt (homozygous recessive)

6. **Calculating Ratios**:
- The total number of homozygous organisms (TT and tt) is 1 (TT) + 1 (tt) = 2.
- The total number of heterozygous organisms (Tt) is 2.
- Therefore, the ratio of homozygous to heterozygous organisms is 2:2, which simplifies to 1:1.

7. **Conclusion**:
The ratio of homozygous to heterozygous organisms in the F2 generation of a monohybrid cross is 1:1.

### Final Answer:
The ratio of homozygous to heterozygous organisms in the F2 generation of a monohybrid cross is **1:1**.

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