Mendel proposed that the factor controlling any character is discrete and independent. This proposition was based on which of the following observations ?

Options

A. Offsprings of `F_3` generation of a cross made between the plants having two contrasting characters show blended characters of its parents
B. Offsprings of a cross made between the plants having two contrasting characters shows only character without any blending
C. Offsprings of self - pollination of `F_1` parents with the same contrasting characters show blended characters of its parents
D. Offspring of cross - pollination of parental generation having three contrasting characters show only one character with blending.

Answer

To answer the question regarding Mendel's proposition that the factor controlling any character is discrete and independent, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Mendel's Work**: Gregor Mendel conducted experiments on pea plants (Pisum sativum) to understand how traits are inherited. He focused on seven contrasting traits, such as plant height, flower color, and seed shape.

**Hint**: Remember that Mendel used pea plants for his experiments because they have easily observable traits and can be cross-bred.

2. **Monohybrid Cross**: Mendel performed monohybrid crosses, which involve a single trait. For example, he crossed a pure tall plant (TT) with a pure dwarf plant (tt). The first generation (F1) offspring were all tall (Tt), demonstrating the dominance of the tall trait.

**Hint**: A monohybrid cross involves two parents differing in one trait. Focus on the dominant and recessive alleles.

3. **F2 Generation and Segregation**: When Mendel self-fertilized the F1 generation (Tt x Tt), he observed a 3:1 phenotypic ratio in the F2 generation: three tall plants to one dwarf plant. This indicated that the alleles segregate during gamete formation.

**Hint**: The 3:1 ratio is key evidence of segregation. Think about how alleles separate during gamete formation.

4. **Law of Segregation**: Mendel formulated the Law of Segregation, which states that during the formation of gametes, the two alleles for a trait separate from each other. This means that each gamete carries only one allele for each trait.

**Hint**: The Law of Segregation explains how traits can reappear in a recessive form in subsequent generations.

5. **Discrete Factors**: Mendel concluded that the factors (now known as genes) controlling traits are discrete and do not blend. This means that even when both alleles are present in a heterozygote, they remain separate and distinct.

**Hint**: Discrete factors imply that traits do not mix; they are either expressed as one phenotype or the other.

6. **Conclusion**: Mendel's observations led him to propose that factors controlling traits are independent and discrete, based on the results of his crosses and the ratios observed in the offspring.

**Hint**: The independence of alleles is crucial for understanding inheritance patterns.

### Final Answer:
Mendel's proposition that the factor controlling any character is discrete and independent was based on his observations from monohybrid crosses, particularly the fact that traits did not blend and that alleles segregated independently during gamete formation.