Explanation:

The recombination frequency between genes can be used to determine their linear arrangement on a chromosome. Recombination frequency is a measure of how often two genes are separated during the process of genetic recombination.

Given Information:

- Recombination frequency between gene p and gene q is 18%.
- Recombination frequency between gene p and gene r is 8.4%.
- Recombination frequency between gene q and gene r is 9.6%.

Analysis:

To determine the linear arrangement of these genes on the chromosome, we need to consider the recombination frequencies between each pair of genes.

Let's start by considering the recombination frequency between gene p and gene q, which is 18%.

Recombination frequency between p and q:

- A recombination frequency of 18% indicates that 18% of the offspring produced from a cross between individuals with different alleles for these genes will show recombination between p and q.
- This suggests that p and q are relatively far apart on the chromosome, as a higher recombination frequency indicates a greater physical distance between genes.

Next, let's consider the recombination frequency between gene p and gene r, which is 8.4%.

Recombination frequency between p and r:

- A recombination frequency of 8.4% indicates that 8.4% of the offspring produced from a cross between individuals with different alleles for these genes will show recombination between p and r.
- This suggests that p and r are relatively close together on the chromosome, as a lower recombination frequency indicates a smaller physical distance between genes.

Finally, let's consider the recombination frequency between gene q and gene r, which is 9.6%.

Recombination frequency between q and r:

- A recombination frequency of 9.6% indicates that 9.6% of the offspring produced from a cross between individuals with different alleles for these genes will show recombination between q and r.
- This suggests that q and r are relatively far apart on the chromosome, as a higher recombination frequency indicates a greater physical distance between genes.

Conclusion:

Based on the analysis of the recombination frequencies, the correct linear arrangement of these genes on the chromosome is q, r, p (option D). This arrangement is consistent with the relative distances inferred from the recombination frequencies between the genes.