Question

Agrobacterium tumefaciens contains a large plasmid, which induces tumour in the plants. It is termed as

• A. Ti plasmid
• B. Ri plasmid
• C. Recombinant plasmid
• D. Shine-Dalgarno sequence

Answer 1

The correct option is A Ti plasmid

1.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.

2.When Ti plasmid transfects the host plant, crown gall tumor is induced, transferring the T-DNA region. Those cells transfected with the T-DNA are induced to grow as well as to produce opines that the bacteria feed on. 3.Agrobacterium rhizogenes is a soil born Gram-negative bacterium, a causative agent of hairy root disease. The plasmid of A. rhizogenes is known as the Ri-plasmid (pRi). The pRi have extensive functional homology with the pTi.

4.A distinct segment(s) of DNA of pRi is transferred to plant genome, during infection, mediated by another segment on the plasmid the virulence (vir) region.

5.The sequence (AGGAGGU) present slightly upstream from the initiation sequence (AUG) on the messenger RNA of prokaryotes is complementary to the 16S ribosomal RNA and is referred to as the Shine-Dalgarno sequence.

6.It recruits the ribosome to the mRNA to initiate protein synthesis. Recombinant plasmid is an engineered plasmid carrying gene of interest from a foreign source. Correct option is A.