GM crops are made through the process collectively termed as genetic engineering. The process of artificially introducing a genetic material from one organism (usually of unrelated species) to another can be summarized in four steps:

1. The specific gene sequence responsible for the desired trait is identified. Once the gene is completely identified and described, it is isolated from the donor organism’s genetic material (DNA) and copies of the gene are made.
   
   Isolation is made possible through the utilization of specific enzymes called restriction enzymes, which cut the DNA at very specific locations, and ligases, which join DNA fragments at specific locations.
   
   
2. The next problem is how to transfer the isolated gene and incorporate it to the recipient organism’s DNA. Currently, there are two types of delivery system.
   
   The physical method involves literally forcing the cell wall or membrane of the target organism’s cell to open so that the isolated gene can be integrated into the genetic material in the nucleus. This is done by accelerating the metal-coated gene into the target cells of the recipient organism through microprojectile bombardment (also called biolistics). The instrument used to perform this process is called the gene gun. Metals used in gene guns are heavy metals, usually gold or tungsten.
   
   The other delivery system uses what is called the plasmid vector. The isolated gene is inserted into the plasmid of Agrobacterium tumefaciens, which naturally transfers it to the genetic material of the host. The plasmid of this type is also called tumor-inducing plasmid, or Ti-plasmid.
   
   
3. The new gene should now be integrated in the recipient crop plant’s DNA. However, the success rate for any delivery system is not absolutely assured, so that selection methods are conducted to see which cells have successfully received the transgene (the gene responsible for the new desired trait).
   
   By micropropagation, the transformed cells regenerate into fertile plants, and the new genetic information in the recipient cells is then expressed. In addition, the transgene must be expressed in the tissue where it is intended to be expressed and at the intended time.
   
   
4. It is not enough that the new gene is expressed in the transformed crop plant. The inserted gene must also be stable and must be capable of being transmitted to the next generation.