Question

Chromosomal aberration in which there is no loss or gain of gene complement is

• A. deletion
• B. duplication
• C. inversion
• D. translocation

Hint:

{Memory Trick:}

• {Deletion} → Loss of chromosome segment
• {Duplication} → Extra copy of chromosome segment
• {Inversion} → Segment flips \(180^\circ\) but genes remain the same
• {Translocation} → Segment moves to another chromosome

Think of {inversion} like flipping a word in a sentence — the letters remain the same, but their order changes.

Answer 1

The Correct Option is C

Concept:
Chromosomal aberrations are structural alterations in chromosomes that occur due to breakage and abnormal rejoining of chromosome segments. These changes can affect the arrangement or quantity of genetic material. Chromosomal aberrations are generally classified into two major types:

• Unbalanced aberrations – These involve a loss or gain of genetic material. Examples include deletion and duplication.
• Balanced aberrations – These involve a rearrangement of chromosome segments without changing the total amount of genetic material. Examples include inversion and some forms of translocation.

Step 1: Understanding deletion and duplication.

• Deletion: A portion of a chromosome is lost during breakage, resulting in the loss of genes.
• Duplication: A segment of the chromosome is copied and repeated, leading to an increase in gene number.

Both of these changes alter the total genetic content of the chromosome.
Step 2: Understanding inversion.
In an inversion, a segment of the chromosome breaks off, rotates by \(180^\circ\), and reattaches to the same chromosome. In this process:

• The same genes remain present.
• Only the order or orientation of genes changes.
• There is no net loss or gain of genetic material.

Thus, inversion is considered a balanced chromosomal rearrangement.
Step 3: Understanding translocation.
In translocation, a segment from one chromosome attaches to a non-homologous chromosome. Some translocations may be balanced (no gene loss), but they involve exchange between different chromosomes. Among the given structural aberrations, the most typical example where the gene complement remains unchanged within the same chromosome is inversion. Final Answer: \(\boxed{\text{Inversion}}\)