What do you call a genetically identical copy created from the DNA of a donor organism?

The correct term for a genetically identical copy created from the DNA of a donor organism is "clone." Cloning is a process that results in an organism, cell, or piece of genetic material that is genetically identical to the original donor. This can occur naturally, as in the case of identical twins, or can be performed artificially through various techniques, such as somatic cell nuclear transfer.

Cloning is significant in many fields, including medicine and agriculture, as it offers the potential to replicate organisms with desirable traits or to help in the study of genetic diseases. In this case, since the term specifically refers to an organism or entity being identical to the donor at the genetic level, "clone" is the most accurate term among the options provided.

Other terms like gene therapy, hybrid, and genetic marker refer to different concepts. Gene therapy relates to the modification of genes to treat or prevent disease. A hybrid indicates the offspring produced by mating two genetically different parents. A genetic marker is a specific sequence of DNA that can be used to identify individuals or species. None of these terms describe the action of creating a genetically identical organism from a donor's DNA.