Transposon insertion effect: When a transposable element jumps into an otherwise functional gene, what is the most common immediate effect on that gene’s expression?

Introduction / Context:
Transposable elements (TEs) are mobile DNA sequences that can insert into new genomic locations. Their insertions often disrupt genes or regulatory regions, providing powerful mutagenesis tools in genetics and functional genomics and explaining many natural variants.

Given Data / Assumptions:

• A functional gene has intact coding and regulatory sequences.
• A TE inserts within the gene body or key regulatory DNA.
• We consider the typical immediate effect of such an insertion.

Concept / Approach:
Insertion within exons introduces extra sequence that can cause frameshifts, premature stops, or aberrant splicing. Insertions into promoters or enhancers can abolish or misregulate transcription initiation. The net effect is usually loss or severe reduction of correct expression, observable as a knockout or knockdown phenotype.

Step-by-Step Solution:

Verification / Alternative check:
TE tagging experiments recover null phenotypes from insertions within genes; reverting insertions or precise excision restores expression, confirming causality.

Why Other Options Are Wrong:

• Initiating or propagating “correct” transcription is rare; TEs may contain promoters but usually misexpress rather than fix expression.
• “Initiating some genetic codes” is not meaningful; codon usage is unaffected directly by TE presence.
• Translation accuracy changes are not a typical consequence of DNA insertions.

Common Pitfalls:
Assuming all insertions are loss-of-function; some in introns may be tolerated, and some TEs upregulate nearby genes, but the common, testable outcome is disruption.

Final Answer:
Blocking correct transcription (loss of normal expression)