Question

Which of the following is correct statement for Ac/Ds transposon family?

• A. RNA transposons that lack LTRs
• B. RNA transposons with LTRs
• C. DNA transposons
• D. Tn3 type transposons

Hint:

Ac/Ds = McClintock = Maize = DNA Transposon.
Class I = RNA (Copy/Paste).
Class II = DNA (Cut/Paste).
Think: "DNA jumps directly, RNA takes a detour through a transcript."

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The Ac/Ds system was the first transposable element system discovered (by Barbara McClintock in maize). The question asks for its broad classification within the types of "jumping genes."

Step 2: Detailed Explanation:

• Class II Transposons: Transposable elements are divided into two classes. Class I (Retrotransposons) move via an RNA intermediate. Class II (DNA Transposons) move directly from one DNA site to another using a "cut-and-paste" mechanism.

• Ac/Ds System: The Ac (Activator) and Ds (Dissociation) elements are classic DNA transposons.

• Autonomous vs. Non-autonomous:
- Ac is autonomous; it codes for the enzyme transposase required for movement.
- Ds is non-autonomous; it is a mutated version of Ac that has lost the transposase gene. It can only "jump" if an Ac element is present in the same cell to provide the enzyme.

• Structural features: They are characterized by Terminal Inverted Repeats (TIRs) at their ends, which are recognized by the transposase enzyme. They do not involve RNA intermediates or Reverse Transcriptase.

• Analysis of other options: Options A and B refer to Class I retrotransposons (like LINEs or LTR-retrotransposons). Option D refers to specific bacterial transposons.

Step 3: Final Answer:
The Ac/Ds family consists of DNA-based transposable elements that move using a transposase-mediated mechanism.