If two genes in a dihybrid cross were located on the same chromosome, the proportion of parental gene combinations will be:

Options

A. Lower than the non-parental type.
B. Remains same as the non-parental type.
C. Higher than the non-parental type.
D. No change

Explanation

To solve the question regarding the proportion of parental gene combinations in a dihybrid cross where two genes are located on the same chromosome, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Dihybrid Cross**:
A dihybrid cross involves two traits that are being studied simultaneously. In this case, we are considering two genes, each with two alleles.

2. **Identifying the Genes and Alleles**:
Let's assume we have two traits:
- Trait 1: Plant height (Tall = T, Dwarf = t)
- Trait 2: Seed shape (Round = R, Wrinkled = r)
The parental combinations could be Tall Round (TR) and Dwarf Wrinkled (tw).

3. **Linkage of Genes**:
Since the question states that the two genes are located on the same chromosome, they are considered linked genes. This means they tend to be inherited together rather than assorting independently.

4. **Parental and Non-parental Combinations**:
In a typical dihybrid cross of unlinked genes, we would expect a 9:3:3:1 ratio of offspring phenotypes. However, when genes are linked, the parental combinations (TR and tw) will be more frequent than the non-parental combinations (Tr and tR).

5. **Proportion of Parental Combinations**:
Because the genes are linked, the proportion of parental gene combinations will be higher than that of non-parental combinations. The exact proportion can vary based on the distance between the genes on the chromosome, but generally, we can conclude that the parental combinations will dominate.

6. **Conclusion**:
Therefore, in a dihybrid cross where two genes are located on the same chromosome, the proportion of parental gene combinations will be greater than 50%.