Question

In Ti-plasmid, which of the following is removed?
A.Auxin gene
B.Virulent gene
C.Cytokinin gene
D.Auxin & cytokinin gene

Answer 1

Hint: Ti-plasmid belongs to the family of plasmids carried by species of Alphaproteobacteria. This plasmid family is defined by the presence of a conserved DNA region known as repABC gene cassette which helps in the replication of plasmid, separation of the plasmid to daughter cells during cell division as well as maintenance of the low number copies of the plasmid cells.

Complete answer:Auxin gene- There are three genes that encode enzymes to synthesize phytohormones tryptophan and indole acetamide which is responsible for the synthesis of auxin.
Virulent gene- Virulence genes are very unique regions and are very important components of the Ti plasmid. This region contains at least ten organized 35kb sized operons. Most of the vir operons are involved in T DNA transfer.
Cytokinin gene- The plant pathogenic bacterium Agrobacterium tumefaciens causes crown gall by incorporation of their transferred DNA into the plant's genome. Acetosyringone(AS) induced tumor-inducing (Ti) plasmid gene and tzs(trans zeatin) which regulates the synthesis of plant hormone cytokinin.
Hence the correct answer is option B, the virulent gene.

Additional information:
Agrobacterium and related Agrobacterium species are known as plant pathogens since the beginning of the 20th century. However, in the past two decades, only the Agrobacterium ability to transfer DNA to plant cells has been taken as an advantage for plant genetic engineering. It is used to create genetically engineered plants for biotechnology purposes.

Note: Ti plasmid or tumor-inducing plasmid is a plasmid only often used as a part of genetic equipment that Agrobacterium rhizogenes and Agrobacterium tumefaciens use to transfer their genetic material to plants.
The major advantage of this plasmid is that it has virulence genes, which helps to copy one or more segments of the plasmids to be transferred into plant cells and then can be integrated into the plant genome.