Independent assortment of genes does not take place when:

Options

A. Genes are located on homologous chromosomes
B. Genes are linked and located on same chromosome
C. Genes are located on non-homologous chromosome
D. All the above

Answer

To solve the question "Independent assortment of genes does not take place when:", we need to analyze the options provided and understand the concept of independent assortment in genetics.

### Step-by-Step Solution:

1. **Understanding Independent Assortment**:
- Independent assortment is a principle of genetics proposed by Gregor Mendel. It states that the alleles of different genes segregate independently of one another when forming gametes. This means that the inheritance of one trait will not affect the inheritance of another trait.

2. **Analyzing the Options**:
- **Option A**: Genes are located on homologous chromosomes.
- This is incorrect because genes on homologous chromosomes can assort independently if they are not linked.

- **Option B**: Genes are linked and located on the same chromosome.
- This is correct. When genes are linked (i.e., they are close together on the same chromosome), they tend to be inherited together and do not assort independently.

- **Option C**: Genes are located on non-homologous chromosomes.
- This is incorrect because genes on non-homologous chromosomes can assort independently.

- **Option D**: All of the above.
- This is also incorrect because only option B is true regarding the lack of independent assortment.

3. **Conclusion**:
- The correct answer is **Option B: genes are linked and located on the same chromosome**. This is the scenario where independent assortment does not occur.

### Final Answer:
Independent assortment of genes does not take place when genes are linked and located on the same chromosome.

---