Vectors for cloning genes in plants and animals - Practice Questions & MCQ

Vectors for cloning genes in plants:

• Agrobacterium tumefaciens is a soil-borne, Gram-negative bacterium. 
• A. tumefaciens is a phytopathogen and is treated as nature’s most effective plant genetic engineer.
• There are mainly two species of Agrobacterium:
  • A. tumefaciens that induce crown gall disease.
  • A. rhizogenes that induce hairy root disease.
• Crown gall formation occurs when the bacterium releases its Ti plasmid (tumour- inducing plasmid) into the plant cell cytoplasm. 
• A fragment (segment) of Ti plasmid, referred to as T-DNA, is actually transferred from the bacterium into the host where it gets integrated into the plant cell chromosome (i.e. host genome). 
• Thus, crown gall disease is a naturally evolved genetic engineering process.
• The tumour inducing (Ti) plasmid of Agrobacterium tumefaciens has now been modified into a cloning vector which is no more pathogenic to the plants but is still able to use the mechanisms to deliver genes of our interest into a variety of plants. 

Vectors for cloning genes in animals:

• Similarly, retroviruses in animals have the ability to transform normal cells into cancerous cells.
• Retroviruses have also been disarmed and are now used to deliver desirable genes into animal cells.