Mendel has a difficulty inexplaining the linked characters due to :

Options

A. Law of dominance
B. Law of segregation
C. Law of independent assortment
D. All the above

Answer

### Step-by-Step Solution:

1. **Understanding Linked Characters**:
- Linked characters refer to traits that are inherited together because their genes are located close to each other on the same chromosome. This means they do not segregate independently during gamete formation.

2. **Mendel's Experiments**:
- Gregor Mendel conducted experiments using pea plants (Pisum sativum) to understand inheritance patterns. He focused on traits such as seed shape and seed color.

3. **Dihybrid Cross**:
- Mendel performed a dihybrid cross between a plant with dominant traits (round shape and yellow color) and a plant with recessive traits (wrinkled shape and green color). The genotypes of the parents were RRYY (round yellow) and rryy (wrinkled green).

4. **F1 Generation**:
- The F1 generation consisted of all hybrids (RrYy), which displayed the dominant phenotypes (round and yellow).

5. **F2 Generation and Phenotypic Ratios**:
- When Mendel selfed the F1 hybrids, he observed a phenotypic ratio of 9:3:3:1 in the F2 generation, which included both parental phenotypes and non-parental (recombinant) phenotypes.

6. **Law of Independent Assortment**:
- Based on his observations, Mendel formulated the Law of Independent Assortment, which states that alleles for different traits segregate independently of one another during gamete formation.

7. **Limitations of Mendel's Law**:
- Mendel's law does not account for linked genes. He assumed that all genes assort independently, which is not always true when genes are located on the same chromosome.

8. **Conclusion**:
- Mendel could not explain linked characters because he believed in the independence of gene assortment. He did not observe linkage in his experiments with garden peas, leading to the conclusion that genes are separate units.