Describe two vectorless methods of gene transfer used in rDNA technology

Explanation

The term direct or vector less transfer of DNA is used when the foreign DNA is directly introduced into the genome. (a) Electroporation : Electroporation basically involves the use of high field strength, electrical impulses to reversibly permeabilize the cell membranes for the uptake of DNA. This technique can be used for the delivery of DNA into intact plant cells and protoplasts. Now-a-days, intact cells, callus cultures and immature embryos can be used with suitable pre-and post-electroporation treatments. Electroporation has been successfully used for the production of transgenic plants of many cereals e.g., rice, wheat, maize. (b) Particle Bombardment (Biolistics) : Particle (or micro projectile) bombardment is the most effective method for gene transfer. This method is versatile due to the fact that it can be successfully used for the DNA transfer in mammalian cells and microorganisms. In this the gold or tungsten beads coated with DNA are bombarded with high velocity on the host tissue. The foreign gene gets incorporated in host DNA. (c) Other methods include micrainjection where a micropipette is used to inject the DNA into the nucleus. Transformation of bacteria can also be done by making the bacteria more competent to take up the foreign gene by placing them in cold calcium chloride or by heat stock. Liposome mediated transfer can also be used.