Which one of the following information is essential to determine the genetic map distance between two genes located on the same chromosome ?

Options

A. Length of the particular chromosome
B. Number of genes present in the particular chromosome
C. Number of nucleotied in the particular sequence
D. Percentage of crossing over or recombinant frequency between two genes

Answer

To determine the genetic map distance between two genes located on the same chromosome, we need to focus on the concept of recombinant frequency. Here’s a step-by-step solution to the question:

### Step-by-Step Solution:

1. **Understanding Genetic Mapping**: Genetic mapping involves determining the relative positions of genes on a chromosome. The distance between genes can be inferred from how often they are inherited together versus how often they are separated due to crossing over.

2. **Identifying Key Concepts**:
- Genes located on the same chromosome can be linked or unlinked.
- Linked genes tend to be inherited together, while unlinked genes assort independently.

3. **Importance of Crossing Over**: During meiosis, crossing over can occur between homologous chromosomes, leading to the exchange of genetic material. This process can separate linked genes, resulting in recombinant offspring.

4. **Recombinant Frequency**: The recombinant frequency is a measure of the likelihood that two genes will be separated during crossing over. It is calculated using the formula:
\[ \text{Recombinant Frequency} = \frac{\text{Number of Recombinants}}{\text{Total Offspring}} \times 100\% \]
This frequency provides a direct measure of the genetic distance between the two genes.

5. **Conclusion**: To determine the genetic map distance between two genes on the same chromosome, the essential information needed is the **percentage of crossing over or recombinant frequency** between the two genes.

### Final Answer:
The essential information to determine the genetic map distance between two genes located on the same chromosome is the **percentage of crossing over or recombinant frequency between the two genes**.

---