In monohybrid cross, pure homozygous plants will be

Options

A. One
B. Two
C. Three
D. Four

Answer

### Step-by-Step Solution:

1. **Understanding Monohybrid Cross**:
- A monohybrid cross involves the inheritance of a single trait, which can be represented by two contrasting alleles. In Mendel's experiments, he used pea plants to study traits such as stem height.

**Hint**: Remember that a monohybrid cross focuses on one trait and its two alleles.

2. **Identifying the Alleles**:
- For the trait of stem height, we have two alleles:
- Dominant allele (T) for tall plants.
- Recessive allele (t) for dwarf plants.

**Hint**: Dominant alleles mask the expression of recessive alleles.

3. **Setting Up Parental Generation**:
- In a monohybrid cross, we start with two pure homozygous parents:
- One parent is homozygous dominant (TT) - tall.
- The other parent is homozygous recessive (tt) - dwarf.

**Hint**: Pure homozygous plants have identical alleles for the trait being studied.

4. **F1 Generation**:
- When we cross these two parents (TT x tt), all offspring in the F1 generation will be heterozygous (Tt) and exhibit the dominant phenotype (tall).

**Hint**: The F1 generation will only show the dominant trait.

5. **F2 Generation**:
- When the F1 generation (Tt) self-fertilizes (Tt x Tt), we can determine the genotypes of the F2 generation using a Punnett square.
- The possible combinations are:
- TT (homozygous dominant)
- Tt (heterozygous)
- Tt (heterozygous)
- tt (homozygous recessive)

**Hint**: Use a Punnett square to visualize the combinations of alleles in the offspring.

6. **Counting the Genotypes**:
- From the Punnett square, we find:
- 1 TT (homozygous dominant)
- 2 Tt (heterozygous)
- 1 tt (homozygous recessive)

**Hint**: Count the number of homozygous and heterozygous plants separately.

7. **Determining the Number of Pure Homozygous Plants**:
- In the F2 generation, we have:
- 1 homozygous dominant (TT)
- 1 homozygous recessive (tt)
- Therefore, there are a total of 2 pure homozygous plants in the F2 generation.

**Hint**: Remember to include both homozygous dominant and homozygous recessive when counting.

### Final Answer:
In a monohybrid cross, the number of pure homozygous plants in the F2 generation is **2** (1 TT and 1 tt).