Association of parental combination of characters in offspring in excess of dihybrid cross is due to

Options

A. Pseudoalleles
B. Linkage
C. Polygeny
D. Codominance

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the reason for the association of parental combinations of characters in offspring that exceeds what is expected in a dihybrid cross.

2. **Identifying Key Concepts**:
- A dihybrid cross involves two traits, each represented by two alleles.
- The expected ratio in a typical dihybrid cross (without any linkage) is 9:3:3:1.

3. **Exploring the Options**:
- **Pseudo alleles**: These are not relevant to the question as they refer to alleles that do not behave like typical alleles.
- **Linkage**: This refers to genes that are located close together on the same chromosome and tend to be inherited together.
- **Polygeny**: This involves multiple genes influencing a single trait, which does not directly explain the parental combination excess.
- **Co-dominance**: This refers to a situation where both alleles in a heterozygote are fully expressed, which is not related to the inheritance pattern in a dihybrid cross.

4. **Analyzing Linkage**:
- When genes are linked, they do not assort independently during gamete formation. Instead, they tend to be inherited together, leading to an excess of parental combinations in the offspring.
- This explains why in a dihybrid cross, if the genes are linked, the offspring will show more of the parental combinations than the recombinant combinations.

5. **Conclusion**: The correct answer is **linkage**, as it accounts for the observed excess of parental combinations in the offspring of a dihybrid cross.

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