The crossing over between homologous chromosomes never exceeds beyond

Options

A. 0.5
B. 0.75
C. 1
D. 0.85

Answer

To solve the question regarding the maximum extent of crossing over between homologous chromosomes, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Homologous Chromosomes**:
- Homologous chromosomes are pairs of chromosomes that have the same gene sequence, chromosomal length, and centromere location. They are similar in structure and carry genes for the same traits.

**Hint**: Remember that homologous chromosomes are crucial for genetic variation during meiosis.

2. **Definition of Crossing Over**:
- Crossing over is a process that occurs during meiosis where homologous chromosomes exchange segments of genetic material. This increases genetic diversity in the resulting gametes.

**Hint**: Think about how crossing over contributes to genetic variation in offspring.

3. **Maximum Extent of Crossing Over**:
- The extent of crossing over between two homologous chromosomes is quantified as a recombination frequency, which is expressed as a percentage. This frequency indicates how often crossing over occurs between two genes.

**Hint**: Consider the relationship between recombination frequency and genetic distance.

4. **Recombination Frequency Limitations**:
- The maximum recombination frequency between two genes on the same chromosome is 0.5 (or 50%). This means that if two genes are far apart on the same chromosome, they assort independently, and the maximum observed frequency of recombination will not exceed this value.

**Hint**: Recall that a recombination frequency of 0.5 indicates that genes are assorting independently.

5. **Conclusion**:
- Therefore, the crossing over between homologous chromosomes never exceeds beyond 0.5.

**Final Answer**: The crossing over between homologous chromosomes never exceeds beyond **0.5**.