Which chromosomal aberration reverses the orientation of a chromosome segment without removing or duplicating material?

• A. Deletion
• B. Duplication
• C. Translocation
• D. Inversion

Answer: (D)

The main concept tested is how a chromosomal rearrangement can change orientation without changing the amount of genetic material. An inversion does this: a segment of the chromosome experiences two breaks, the segment is flipped, and then reintegrated in the reverse orientation. No DNA is lost or gained, so the total genetic material remains the same; only the order is altered. This is what distinguishes it from deletions (which remove material) and duplications (which duplicate material). It also differs from translocations, where a piece of chromosome material moves to a different chromosome. So the description fits inversion: reversal of a segment’s orientation without loss or gain of material.