Recombinant DNA is an exciting area of molecular genetics that involves fusing the DNA from two different organisms into one. Recombinant DNA has numerous uses including producing desired protein products, such as human insulin from bacteria, or creating a plant that produces plastic. While today we think of recombinant DNA organisms as being created in a lab, people who have genetic conditions known as chimera and mosaicism are nature's versions of recombinant DNA.
Recombinant DNA Primer
Recombinant DNA techniques are often referred to as genetic engineering. By manipulating genes in an organism, you can induce them to do things they didn't before or get them to stop exhibiting unwanted behaviors. Growing plants with built-in pesticide resistance allows farmers to spray their crops without worry of killing their desired plants, and this is possible by inserting foreign DNA into the plants. The sequence of an organism's DNA is coded for the different proteins the organism needs. So if scientists know of a protein they desire to duplicate, they determine the DNA sequence from the original organism and introduce it in a new organism. So for insulin for diabetic patients, researchers got the sequence of DNA for human insulin and inserted it into some bacteria and now the bacteria produce human insulin.
Chimeras
Some people refer to all recombinant DNA as chimera, but most scientists reserve that term for a specific genetic condition. A Chimera is a Greek mythological beast that is a combination of lion, serpent and goat. Individuals with chimera DNA actually have DNA from two separate individuals. Some of their cells have one type of DNA and the rest have an entirely different DNA sequence. This condition can lead to a variety of physical characteristics, including people with two skin tones or two eye colors or even two hair colors
How Chimeras Occur
The first cell that we all started out as is called the zygote and it is created when the sperm and egg fuse. The one cell becomes two which in turn become four cells and so on. This goes on for a while before there is any thought of cell specialization. In other words, at these early stages, all the cells are identical. Fraternal twins are the result of two separate eggs being fertilized and creating two zygotes. In rare cases, these two developing embryos can collide and fuse into one embryo. When , all the cells just assume they are one embryo and continue dividing normally. When it is time for , when cells start becoming different, it's just happenstance which set of DNA is used for each part of the body.
Mosaics
Mosaics are similar to chimeras with a few differences. Primarily, mosaics start off as one zygote and there is never any fusing with an outside source of DNA. However, at some point during development, a mutation in their DNA occurs, which is more common than you may think. If that mutation does not cause the death of the cell, when it replicates, the new have that mutation. When those two cells replicate, their descendants will carry it and so on down the line. Depending on when the , the mosaicism can be widespread or localized. If this occurs in an adult, the new DNA will likely stay in the area of the initial mutation. If it occurs in a developing embryo, however, roughly half of the mosaics cells will exhibit one type of DNA and the rest will exhibit the other.
Effects of Mosaicism
Mosaicism can have a range of effects from none at all to cancerous cell growth. It all depends on what the DNA mutation was in the first place. DNA is not a perfect molecule and there is a lot of junk information littered in with the good. So if a mutation occurs in the junk areas, there is no effect. There are possibilities that allow for a mutation in good areas that have no effect as well. However, some mutations cause diseases such as sickle-cell anemia and cancer, so the possibilities are endless.
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