If there were only parental combinations in `F_(2)` of a dihybrid cross then Mendel might have discovered :-

Options

A. (a) Independent assortment
B. (b) Atavism
C. (c) Linkage
D. (d) Repulsion

Answer

**Step-by-Step Solution:**

1. **Understanding Dihybrid Cross**: A dihybrid cross involves two traits, where each trait is controlled by different genes. For example, in Mendel's pea plants, he studied seed color (yellow vs. green) and seed shape (round vs. wrinkled).

2. **Parental Generation (P)**: The parental generation consists of true-breeding plants that exhibit the two traits in their pure forms. For instance, one parent could be homozygous for yellow and round seeds (YYRR) and the other for green and wrinkled seeds (yyrr).

3. **F1 Generation**: When the two parental plants are crossed, the F1 generation will show the dominant traits. In this case, all F1 offspring would be heterozygous (YyRr) and exhibit yellow, round seeds due to the dominance of the yellow and round alleles.

4. **F2 Generation**: When the F1 generation is self-fertilized, the F2 generation is produced. According to Mendel's law of independent assortment, we would expect a phenotypic ratio of 9:3:3:1 in the F2 generation, which includes both parental and recombinant types.

5. **Linkage Concept**: If only parental combinations were observed in the F2 generation, it would suggest that the genes for seed color and seed shape are linked, meaning they are located close together on the same chromosome and tend to be inherited together.

6. **Conclusion**: Since Mendel observed both parental and recombinant types in his experiments, he concluded that the genes assort independently. However, if only parental types were present, he might have discovered the concept of linkage, which explains why certain traits are inherited together.

**Final Answer**: If there were only parental combinations in F2 of a dihybrid cross, Mendel might have discovered the concept of **linkage**.

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