Based on observation on monohybrid cross Mendel draw some conclusion. Which of the following is not correct -

Options

A. Characters are controlled by discrete units called factor
B. Factors occur in pairs
C. In a similar pair of factors one member of the pair dominantes the other
D. The postulate of dominance also explains the proportion of `3:1` obtained at the `F_(2)`

Answer

To solve the question regarding Mendel's conclusions from his monohybrid cross observations, we will analyze the statements provided and identify which one is incorrect based on Mendel's principles.

### Step-by-Step Solution:

1. **Understanding Mendel's Conclusions**: Mendel conducted experiments with pea plants and established several fundamental principles of inheritance. He proposed that traits are controlled by discrete units (now known as genes) and that these units come in pairs.

2. **Evaluating the Statements**:
- **Statement 1**: "Characters are controlled by discrete units which are called as factors."
- This is correct. Mendel referred to genes as "factors" and established that they control traits.

- **Statement 2**: "Factors occur in pairs."
- This is also correct. Mendel noted that organisms have two alleles for each trait, one inherited from each parent.

- **Statement 3**: "In a similar pair of factors, one member of the pair dominates the other."
- This statement is misleading. While it is true that in a heterozygous condition (dissimilar pair), one allele can dominate the other, the phrase "in a similar pair" implies that both alleles are the same (e.g., TT or tt), where dominance does not apply as there is no contrasting allele. Thus, this statement is incorrect.

- **Statement 4**: "The postulate of dominance also explains the proportion of 3:1 obtained at F2."
- This is correct. Mendel observed that in the F2 generation of a monohybrid cross, the phenotypic ratio of dominant to recessive traits is approximately 3:1.

3. **Conclusion**: Based on the evaluation of the statements, the third statement is the one that is not correct according to Mendel's conclusions.

### Final Answer:
The statement that is not correct according to Mendel is: "In a similar pair of factors, one member of the pair dominates the other."

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