which of the following statements is not true of two genes that show 50 % recombination frequency ?

Options

A. The genes are tightly linked
B. The genes show independent assortment
C. If the genes are present on the same chromosome, they undergo more than one crossovers in every meiosis
D. The genes may be on different chromosomes

Answer

To determine which statement is not true regarding two genes that show 50% recombination frequency, we can analyze the options provided based on our understanding of genetic recombination.

### Step-by-Step Solution:

1. **Understanding Recombination Frequency**:
- Recombination frequency refers to the percentage of offspring that exhibit a combination of traits different from either parent due to genetic recombination during meiosis.
- A 50% recombination frequency indicates that the genes are either on different chromosomes or are far apart on the same chromosome.

2. **Analyzing the Options**:
- **Option A**: "The genes are tightly linked."
- This statement is **not true**. A 50% recombination frequency suggests that the genes are loosely linked or possibly on different chromosomes.

- **Option B**: "The genes show independent assortment."
- This statement is **true**. Genes that assort independently are typically those that are not closely linked, which aligns with a 50% recombination frequency.

- **Option C**: "If the genes are present on the same chromosome, they undergo more than one crossover in every meiosis."
- This statement is **true**. When genes are on the same chromosome and are far apart, multiple crossovers can occur, leading to a higher recombination frequency.

- **Option D**: "The genes may be on different chromosomes."
- This statement is **true**. A recombination frequency of 50% can indicate that the genes are located on different chromosomes.

3. **Conclusion**:
- The statement that is not true is **Option A**: "The genes are tightly linked." This is incorrect because a 50% recombination frequency indicates that the genes are either loosely linked or on different chromosomes.

### Final Answer:
The statement that is not true is **Option A**: "The genes are tightly linked."