The Ti plasmid is often used for making transgenic plants. This plasmid is found in
A
Rhizobium of the roots of leguminous plants
B
Agrobacterium
C
Yeast as a 2 $\mu m$ plasmid
D
Azotobacter
The answer is B.
Solution
Ti (tumour-inducing) plasmid is found in the soil bacterium Agrobacterium tumefaciens, which causes crown gall in many dicot plants. A part of this plasmid, the T-DNA, is naturally transferred into the plant genome, where it causes tumours. Scientists remove the tumour-causing genes (disarming the plasmid) and insert the desired gene into the T-DNA. The modified Ti plasmid then acts as a vector to carry useful genes into plants, producing transgenic plants. Yeast carries the 2 $\mu m$ plasmid, which is different; Rhizobium and Azotobacter are nitrogen-fixing bacteria. So the Ti plasmid is found in Agrobacterium.
ConceptTi plasmid of Agrobacterium tumefaciens
Biotechnology: Principles and Processes in past papers
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