Hint: It is used as a clone vector in biotechnology as it extracts tumor inducing genes from the host. It helps insert a foreign gene of interest in the target DNA.
Complete Answer: Plasmid is a small, spherical, double-stranded DNA molecule that is distinct from the chromosomal DNA of a cell. Plasmids usually occur in bacterial cells and also occur in certain eukaryotic cells. Genes carried in plasmids also have genetic benefits for bacteria, such as resistance to antibiotics.
Agrobacterium tumefaciens is a tumour inducing (Ti) plasmid that has been transformed into a clone vector that is able to use pathways to deliver genes of interest to a number of plants. If a gene or DNA fragment has been attached to an effective vector, it is passed to a bacterial, plant or animal host where it is multiplied.
In plant genetic engineering, Ti plasmid can be used to deliver foreign genes to plant cells. When a plant is infected by the bacteria, a portion of the Ti plasmid known as T DNA is passed to a plant chromosome. As the T DNA is expressed as part of the genome, it allows the plant cell to divide and expand abnormally. The Ti plasmid containing the modified T DNA region will then be used to inject the desired genes into plant chromosomes.
Note:Agrobacterium tumefaciens a pathogen of many dicot plants that is capable of transmitting a piece of DNA known as 'T-DNA' to turn normal plant cells into tumours and guide these tumour cells to generate the chemicals produced by the pathogen.