Question

The Ti plasmid and its T-DNA have been genetically modified for use as a vector for the insertion of recombinant DNA into plant chromosomes to prevent dicots from tumor diseases. The source of Ti plasmid is:

• A. Asparagus sp.
• B. Arthrobacter luteus
• C. Aspergillus niger
• D. Agrobacterium tumefaciens

Hint:

Think of Agrobacterium tumefaciens as "nature's genetic engineer." The name itself gives a clue: {tumefaciens} means "tumor-making," which refers to the crown gall disease caused by its \textbf{Ti} (Tumor-inducing) plasmid.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The Ti (Tumor-inducing) plasmid is a naturally occurring plasmid widely used in plant genetic engineering. This question seeks its natural origin.
Step 2: Detailed Explanation:


The Ti plasmid is located within the soil bacterium Agrobacterium tumefaciens.

This bacterium is a plant pathogen, causing crown gall disease, identified by tumor formation on plants, especially dicots.

Agrobacterium naturally introduces a portion of its Ti plasmid, the T-DNA (transfer DNA), into the plant's genome.

Scientists utilize this natural transfer by modifying the Ti plasmid (removing tumor-causing genes) and inserting a desired gene into the T-DNA. The altered Agrobacterium acts as a vector, delivering the gene into plant cells.

The remaining options are incorrect: Asparagus is a plant, Arthrobacter is a different soil bacterium, and Aspergillus is a fungus.

Step 3: Final Answer:
Agrobacterium tumefaciens is the source of the Ti plasmid.