Question #65537. Asked by
crazycube.
Last updated Dec 02 2017.
Interspecies breeding (sometimes called cross breeding1) is the act of creating offspring from two different species. It should not be confused with the chimera which involves more of a Frankenstein-type process of gene splicing, cell modification, implantation, and embryo modification. While the creation and study of hybrid plants has been ongoing for hundreds of years, this writeup deals with hybrid species created by cross breeding in the animal kingdom - specifically mammals, however the concepts themselves cross these borders.http://everything2.org/index.pl?node_id=1528852
Interspecies breeding is a very complex subject. Obviously it is not possible to mate any animal with any other animal to produce a strange new creature. If you've learned anything from South Park, you will know that "pig and elephant DNA just won't splice". It is commonly believed that for two species to be able to interbreed, they must have the same number of chromosomes. While this is true in most cases there are many exceptions. For example, a horse (64 chromosomes) and a zebra (44 chromosomes) can produce viable offspring. If the animals have a different number of chromosomes, the animal with the smaller number must be the male (e.g., a male zebra and a female horse could produce a foal, but a female zebra could not be impregnated by a male horse). What is most important is that the chromosomes that do match up are homologous. What determines this homology at the cellular level is beyond the scope of this writeup.
In general, cross bred animals are sterile. This is typically related to the fact that even if the chromosomes match up enough to create the offspring, there are still genetic problems that cause the hybrid to be unable to produce children. In cases where then animal can (medically) produce viable eggs or sperm; it again becomes a problem of matching chromosomes with some other species. This is not to say that no crossbred animal can mate, it is just rare.
Most cross breeding occurs between animals in the same Genus. There have been cases where offspring has been produced between animals in different genera but in the same family. However, this is uncommon, and has caused some scientists to question whether the classifications of these animals are correct in the current system.