Question

Which of the following mechanism is not causing somaclonal variations?

• A. Numerical change in chromosome number
• B. Gene mutations
• C. Gene amplification
• D. Gene transcription

Hint:

Variation means the "Recipe" (DNA) has changed. Transcription is just "Reading" the recipe—it doesn't change the instructions!

Answer 1

The Correct Option is D

Concept: Somaclonal variation refers to permanent, heritable genetic changes that occur during the in vitro culture process. For a change to be considered a "variation," it must involve an alteration of the genetic blueprint or its stable inheritance.

Step 1: Analyzing Genetic Alterations.
Numerical changes in chromosomes (1) (like aneuploidy or polyploidy), Gene mutations (2) (point mutations or deletions), and Gene amplification (3) (increasing the number of copies of a specific gene) all involve physical changes to the DNA sequence or structure. These are fundamental drivers of somaclonal variation.

Step 2: Defining Gene Transcription.
Gene transcription (4) is the normal, routine biological process of copying a segment of DNA into RNA. It is a part of standard gene expression. Transcription is temporary and occurs in every living cell as it functions.

Step 3: Conclusion.
Because transcription does not alter the underlying DNA sequence or create a permanent heritable change, it is not a mechanism of somaclonal variation. It is simply a sign that the cell is alive and active.