The physical association of the two genes on chromosome is called

Options

A. linkage
B. recombination
C. crossing over
D. segration

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the term that describes the physical association of two genes on a chromosome.

2. **Identifying Key Terms**: The key terms here are "physical association," "two genes," and "chromosome."

3. **Recalling Relevant Concepts**: In genetics, the term that describes the physical proximity of genes located on the same chromosome is known as "linkage."

4. **Historical Context**: The concept of linkage was introduced by Thomas Hunt Morgan, who studied the inheritance patterns of traits in fruit flies (Drosophila melanogaster).

5. **Defining Linkage**: Linkage refers to the tendency of genes that are located close to each other on the same chromosome to be inherited together during the process of meiosis.

6. **Eliminating Incorrect Options**:
- **Recombination**: This term refers to the generation of new allele combinations, which does not directly describe the physical association of genes.
- **Crossing Over**: This is the process where segments of DNA are exchanged between homologous chromosomes, but it is not the term for the physical association of genes.
- **Segregation**: This refers to the separation of alleles during gamete formation, not the physical association of genes on a chromosome.

7. **Conclusion**: The correct answer to the question is "linkage."

**Final Answer**: The physical association of the two genes on a chromosome is called **linkage**.

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