Question

The tumour inducing capacity of Agrobacterium tumefaciens is located in large extrachromosomal plasmid called as

• A. Ti - plasmid
• B. Ri - plamid
• C. $\lambda$ phage
• D. Plasmid pBR322

Answer 1

The correct option is A Ti - plasmid

Agrobacterium tumefaciens is a soil plant pathogenic bacterium that carries Ti plasmid. It can transfer a particular segment of the tumor-inducing (Ti) plasmid into the nucleus of infected cells. The transferred T-DNA is then integrated into the host genome and transform the cells, inducing crown gall. Agrobacterium rhizogenes is a plant pathogen that causes hairy root disease owing to presence of root-inducing plasmid (Ri). Transformation of host cells with Ri plasmid causes hairy roots; it does not induce tumor. Phages are obligate intracellular parasites that insert their genome into bacterial cell followed by destruction of the cell’s genetic material, replication of viral genome, assembly of new virus particles and their release by lysis of host cell. Plasmid pBR322 is used as cloning vector for $E$. $coli$.