Question: can you genetically mutate a pig and make it green

Claire Shooter answered on 16 Jun 2014:

Absolutely! Well, sort of…
The colour of your average pig depends on how much of a protein called melanin it makes. Pigs, like you, have two copies of each gene in their genome and each gene tells them how to make a particular protein. A pig which has two copies of the melanin gene will be black, a pig with no copies of the melanin gene will be pink, and a pig with one of each will have patches of black and patches of pink.
Theoretically, all you would have to do to make a green pig is remove the melanin gene that makes black bits and replace it with one that makes green pigment instead. Unfortunately, we don’t know of any proteins that make green skin – can you think of any mammals with green skin? It’s easier at the moment to add in a new protein than change an existing one, because we still don’t understand genes that well. While we can’t make a pig green all over (yet) we can make it glow green in the dark! In fact, it was done in 2002 in Taiwan using a gene isolated from a species of glowing jellyfish which fluoresces green when exposed to blue light (it’s imaginatively called Green Fluorescent Protein – GFP). The gene makes a protein which absorbs some of the energy of blue or UV light and reflects the rest back: this changes the light’s wavelength from high energy blue/violet to lower energy green. GFP is used in lots of scientific research so we know a lot about it and how to work it now.
To make glowing green pigs the scientists took some pig cells and grew them in a dish. They then added the gene for making GFP into the cells using a virus. Viruses work by infecting cells, getting into their nucleus and inserting themselves into the cell’s DNA. This means that the cell itself will make the viral genes and produce more copies of the virus. In this instance, the dangerous viral genes had been removed, just leaving the ones that help it get itself into the genome. The dangerous genes were replaced with the gene for GFP. Once the cells were definitely infected, the scientists took a fertilized egg cell from another pig and removed the nucleus (where all the DNA is), replacing it with the nucleus of the infected cell. They then implanted the egg cells into another pig, where they grew into piglets with a yellow tinge. When exposed to UV light, the piglets glowed green!
Green fluorescent protein is actually really useful: if you want to try and add a new gene into an animal, you can add the GFP gene to the same piece of DNA and then you can tell which cells of the animal are expressing the gene because they will also glow green. It can also be stuck to antibodies (small proteins that attach to other proteins based on what shape they are) to identify molecules of interest under a microscope. This is called fluorescence microscopy.
It might seem odd to do an experiment like this, but it has important implications for the future of medicine: imagine if a woman was at risk of having a baby with a genetic disorder and we were able to replace the nucleus of an affected fertilised egg with one that was healthy? What if we could do that in adults who had diseases, or in people who had developed cancers (which are caused by small populations of cells mutating and functioning incorrectly)? With the help of green fluorescent pigs, we are starting to develop techniques like these for some diseases – known as gene therapy.

See these:
Gene therapy
http://ghr.nlm.nih.gov/handbook/therapy/genetherapy
Fluorescent Animals
http://news.nationalgeographic.com/news/2009/05/photogalleries/glowing-animal-pictures/
Molecule of the Month: Green fluorescent protein
http://www.rcsb.org/pdb/101/motm.do?momID=42
Fluorescence microscopy
http://serc.carleton.edu/microbelife/research_methods/microscopy/fluromic.html