Everyday Einstein on the possibility of hybrids, chimeras, and even half-human/half-vampire creatures. Read on!
Ligers and Mules and Geeps, Oh My!
In our previous example, we were assuming that the two organisms involved in this process were from the same species. But what happens if two different species are involved?
There are two terms that are used to refer to an organism that is a mix of two different species: hybrid and chimera (pronounced Kai-mare-uh). Although many people use these terms interchangeably, they have distinct meanings to scientists.
A common example of a hybrid is the mule. In order to create a mule, a reproductive cell of a donkey is fused with the reproductive cell of a horse. The resulting zygote has a mix of donkey and horse DNA. Since every cell of an organism is a copy of the zygote, this means that every cell of the mule contains a mix of horse and donkey DNA.
Some hybrids occur naturally, while others are a result of human intervention. Sometimes that intervention is simply playing matchmaker, (ensuring that the organisms are in the right place at the right time), while other times it involves manual intervention, such as artificial insemination of animals or manual pollination of plants.
Unlike hybrids, chimeras are organisms created by merging non-reproductive cells of two or more different organisms. In 1984 scientists working at Cambridge were able to take cells from a sheep embryo and merge them with cells of a goat embryo. The organism that grew from this amalgamation was a sheep-goat chimera (or “geep” as some people referred to it).
Unlike the mule, where each cell contains a mix of horse and donkey DNA, every cell in the geep is either a sheep cell or a goat cell. This means that parts of the animal looked like a sheep and parts of it looked like a goat. In fact, the name “chimera” comes from a mythological creature mentioned in Homer’s The Iliad, described as having “in the fore part a lion, in the hinder a serpent, and in the midst a goat”.
So to summarize, every cell of a hybrid is genetically identical, and contains a mix of DNA from each of its parents. But each cell of the chimera contains the DNA of one parent or the other, but not both.