Many organisms have been genetically engineered to glow: cats, mice, pigs, monkeys, dogs, and even plants. When a new glowing organism is announced, many people don’t seem to understand or appreciate why it has been done. While there is the inherent “cool” factor with a glowing organism, the technique wasn’t developed just for fun.
Biologists utilize genetic engineering for a variety of purposes. They can learn more about the function of a gene if they suppress or amplify its expression. Some genes are pleiotropic, in that they influence many phenotypes, even if they seem unrelated. For this reason, it is incredibly important to understand where a gene is being expressed, but that is slightly more difficult. For that reason, reporter genes for green fluorescent protein (GFP; which gives certain jellyfish their natural bioluminescence) can be inserted into the genome and produce a visible signal when the desired gene is expressed. This allows the researchers to get visual confirmation that the genetic engineering was successfully completed in the desired location.
The gene that encodes GFP is replicated through polymerase chain reaction (PCR), which essentially works like a Xerox machine for DNA. The environmental conditions coax the DNA into replicating until there is an adequate supply. The DNA is then altered to over express the GFP, which will make it easier to see in the animal model. The GFP gene is combined with promotor and enhancer sequences to ensure the finished product will be inserted into the desired location. The engineered DNA is then inserted into a newly-fertilized egg and researchers will screen the organisms later to select the ones that had successfully taken in and expressed the new gene. The success cases will be mated in order to create a reliable strain of organisms that is homozygous for the transgene and useful for study.
In the case of the Convict chichlid (Amatitlania nigrofasciata), the end result looks something like this: