Transposable elements across taxa Which of the following transposable elements is NOT naturally found in plants (i.e., it is characteristic of animals/humans rather than higher plants)?

Introduction / Context:
Transposable elements are DNA sequences that move within genomes. In genetics and biotechnology, it is important to distinguish plant transposons (e.g., Ac/Ds in maize, Tam elements in snapdragon) from animal-specific elements such as LINE-1 (L1), which are abundant in mammals including humans.

Given Data / Assumptions:

• Ac (Activator) is a classic maize DNA transposon.
• Tam3 is a well-studied plant transposon in Antirrhinum majus.
• L1 (LINE-1) is a long interspersed nuclear element that is characteristic of mammalian genomes.

Concept / Approach:
Match each element to its native, widely documented host lineage. Plant DNA transposons like Ac/Ds and Tam3 operate via a cut-and-paste mechanism using transposase. L1 elements are non-LTR retrotransposons that mobilize via an RNA intermediate and reverse transcription; their canonical representatives are mammalian, not plant, elements.

Step-by-Step Solution:

Verification / Alternative check:
Intro genetics texts and transposon catalogs list Ac/Ds and Tam families in plants and L1 in mammals, confirming the mapping.

Why Other Options Are Wrong:

• Ac and Tam3 are plant elements, so they are not “not found” in plants.
• “All are found in plants” is incorrect because L1 is animal-specific.
• “None of the above” contradicts the above evidence.

Common Pitfalls:
Confusing the broader concept of LINEs (which exist across taxa) with the specific L1 lineage that is mammalian.

Final Answer:
L1 (LINE-1 retrotransposon)