Genetic engineering techniques

Genetic engineering techniques enable modification of the DNA of living organisms. A variety of editing techniques have been developed since DNA's structure was first discovered.

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.

Human directed genetic manipulation began with the domestication of plants and animals through artificial selection in about 12,000 BC. Various techniques were developed to aid in breeding and selection. Hybridization was one way rapid changes in an organisms makeup could be introduced. Hybridization most likely first occurred when humans first grew similar, yet slightly different plants in close proximity. Some plants were able to be propagated by vegetative cloning.X-rays were first used to deliberately mutate plants in 1927. Between 1927 and 2017, more than 3,248 genetically mutated plant varieties had been produced using x-rays.

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