If an aberration causes change in the order of genes on a chromosome but does not alter linkage, it is a case of

Options

A. deletion.
B. inversion.
C. translocation.
D. transposition.

Answer

To answer the question, "If an aberration causes change in the order of genes on a chromosome but does not alter linkage, it is a case of," we need to analyze the concepts involved.

### Step-by-Step Solution:

1. **Understanding Aberration**:
- An aberration refers to a deviation from the normal structure of chromosomes. This can involve changes in the number or structure of chromosomes.

2. **Types of Chromosomal Aberrations**:
- Chromosomal aberrations can be classified into two main categories: structural and numerical aberrations. Structural aberrations involve changes in the structure of chromosomes, while numerical aberrations involve changes in the number of chromosomes.

3. **Change in Gene Order**:
- When the order of genes on a chromosome changes, it indicates a rearrangement of the genetic material. This can occur through various mechanisms such as inversions, translocations, or duplications.

4. **Linkage**:
- Linkage refers to the tendency of genes located close to each other on a chromosome to be inherited together. If the linkage is not altered, it means that the relative positions of the genes that were originally linked remain the same despite the rearrangement.

5. **Identifying the Correct Term**:
- The scenario described in the question indicates that there is a change in the order of genes but the linkage remains intact. This specific type of chromosomal aberration is known as an **inversion**. Inversions occur when a segment of a chromosome is reversed end to end, which changes the order of genes but does not affect their linkage.

### Conclusion:
The answer to the question is that the aberration causing a change in the order of genes on a chromosome without altering linkage is a case of **inversion**.

---