Genetic modification of plants and animals: techniques

Modifying an organism requires altering its DNA: adding, deleting or substituting a string of nucleotides that code for a trait in the mature plant, animal, bacterium or fungus. This can be done directly or by using a vector – an entity that will modify an organism's DNA. Both methods rely on the ability to cleave (cut) DNA at desired locations and ligate (join) pieces of DNA. When a vector is used, the modification is made to the vector's DNA; the vector then modifies the organism's DNA. Use of vectors is common in plant biotechnology, as it also is in medical and environmental biotechnology that involves modifying bacteria. I discuss below the use of an element in the bacterium Agrobacterium tumefaciens as a vector in plant modification. A virus, λ phage, that infects bacteria is commonly used to modify the DNA of bacteria in medical and environmental biotechnology.