Question

Which among the following is not a mobile genetic element?

• A. Insertion sequences
• B. Plasmids
• C. Transposons
• D. Introns

Hint:

Mobile genetic elements are capable of moving between genomic positions or host cells (plasmids, transposons, insertion sequences). Introns are primarily non-coding structural segments within genes that are spliced out during RNA processing.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Mobile genetic elements (MGEs) are segments of DNA that encode enzymes and structural proteins enabling them to move within a genome or transfer between cells.
MGEs play a major role in bacterial evolution, adaptation, and horizontal gene transfer, often carrying genes for antibiotic resistance, bacteriocin production, or sugar metabolism.
Common mobile elements include plasmids, transposons, bacteriophages, and insertion sequences.

Step 2: Detailed Explanation:
Plasmids are extrachromosomal circular DNA molecules that replicate independently and can be transferred between cells via conjugation.
Transposons are segments of DNA that can move from one location to another within a genome, often carrying passenger genes.
Insertion sequences are the simplest mobile genetic elements, containing only the transposase gene required for their own transposition.
Introns are non-coding sequences located within eukaryotic and some prokaryotic genes.
They are transcribed into pre-mRNA but are subsequently spliced out during RNA processing before translation occurs.
Although some specialized introns (such as self-splicing group I and group II introns) can act as mobile elements through a process called homing, general introns are not classified as standard mobile genetic elements.
Instead, they are structural, non-coding regions of genes.

Step 3: Final Answer
Introns are not classified as mobile genetic elements.