CHIMERAS

Let me show you something interesting just before we move away from botany and into Zoology. A few weeks ago, a gardener in Devon, England was harvesting apples from his apple trees and was stunned to discover the apple pictured above. This Golden Delicious apple looks like half of a red apple was attached to half of a green apple. So perfect is the division in color, that some might be tempted to declare it a hoax. But this of course is not the case. The explanation is much more interesting - and bizarre.

This stunning apple is the result of a genetic mutation - a 1,000,000 to 1 occurrence that scientists call a chimera (KI - mera). In Greek mythology, Chimeras were monsters made up of parts from different animals. There are chimeras in the natural world, but they are not made up of parts from different animals. They are made from different combinations of genetic information from the same parents of an animal. Or in this case, a plant.

Chimeras form following the moment of fertilization. Two eggs are fertilized by two sperm, and form two zygotes. Normally, two zygotes will go on to form two distinct individuals. In rare cases though, the two zygotes fuse into a single mega-zygote that goes on to form a single individual containing all of the genetic information from two sperm (or in the case of our apple, two pollen spores) and two eggs. After the resulting zygote's first cell division from one cell to two cells, all future populations of cells and tissue will contain the genetic material and characteristics of the original set of parential genetic material that it has developed from. One side will show characterstics from sperm/egg combo 1, and the other side will result from sperm/egg combo 2. Two cells "split down the middle" so to speak. Then they continue to divide: four, eight, sixteen, thirty two - etc. Up through the creation of an entire organism.

Just to address the question on everyone's mind, no, this does not occur in humans. People are not split down the middle, i.e., brown hair/red hair, light complexion/dark complexion. (Though there are rare instances when odd things do occur. More on that at a later point.....)

Chimeras are indeed rare, but not unheard of. Several years ago while spending a summer in Maine, I visited the "Oceanarium" in Bar Harbor. The prize of that summer's catch was a lobster that had the typical lobster coloring along one side of its body, and a blue color along the other half of its body. The division in coloration ran lengthwise from the head to the tail. This chimera was a star attraction at the Oceanarium, and even made it into the national news. The odds of finding a completely blue lobster are about 2,000,000:1. The odds of finding a chimera in a lobster population is about 1,000,000:1. What were the odds of finding this blue chimera lobster? I'll let you do the math. The probability was small indeed. Even smaller if you figure in the odds of catching it. But even unimaginably small probabilities do make themselves seen when populations are large enough. And in a world that is connected electronically, these discoveries become known and shared instantaineously between continents.

Chimeras serve no adaptive purpose. They are simply the result of random genetic mutations and combinations. Sometimes, 1,000,000 to 1 odds become an individual's 100%.