"Mommy...what is a Zorse?"
What about a wholphin? Or a Ti-tigon? What would your answer be? As suspected these are all examples of hybrid crossings: offspring from when two different, usually closely related, species are crossed.
These hybrids usually have the benefit of greater strength and endurance than their parents (like the Mule for example). More often than not the negatives, such as infertility, are overlooked. But what causes hybrid infertility? Can is be controlled?
There are basically two causes: one being the difference in chromosome number of each parent. If both parents have an equal number chromosomes but differ in amount, (62 in the donkey and 64 in the horse), the offspring will end up with an unequal chromosome number (63 in the Mule). This uneven pairing causes infertility in males.
A less likely cause could be a mutation in a certain gene pair (in any species) called Hmr (Hybrid male rescue) and Lmr (Lethal male rescue). Researchers from the Cornell University in New York suggest that the mutations occurred because of a separation of two subgroups of one species. This allowed the individual gene pairs to develop under different natural pressures. The genes then began coding for proteins that were no longer compatible in the other species. If crossed, infertility, birth defects and even death, could result.
Researches believe this new information can be used to determine how certain species are linked to their ancestors.
Certain questions as to species that do produce fertile offspring or some where only females are fertile are still being investigated.
Posted by: Elisha Mathews, 41385474
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