Bacteria are commonly engineered for research purposes. Typically this is through transformation to add a plasmid containing a gene of interest, but editing of the chromosome is also used. Plants and animals have both been genetically modified for research, agricultural and medical applications. In plants, the most widely inserted genes provide herbicide resistance or insecticidal properties. In animals, the most widely used are growth hormone genes. Finally, genetically modified viruses (such as retroviruses and lentiviruses) are also used as viral vectors to transfer target genes to another organism in gene therapy.
The first step involves choosing and isolating the gene that will be inserted into/removed from the genetically modified organism.
The gene must generally be combined with a promoter and terminator region as well as a selectable marker gene.
Then the genes must be spliced into the target’s DNA. For animals, the gene must be inserted into embryonic stem cells.
The resulting organism must have the presence of the target gene confirmed.
First generation offspring are heterozygous, requiring them to be inbred to create the homozygous pattern necessary for stable inheritance. Homozygosity must be confirmed in second generation specimens, which then become the final product.