Articles about American Pit Bull Terrier
Sometimes two different alleles may be better than one. Consider the major histocompatibility complex (MHC) of the immune system as indicated above. This large group of genes requires high diversity because each on of these individual genes adapts to combat a specific insult to the immune system. Having a variety of MHC alleles is vital to an animals ability to combat any given infection (for instance) or allergen. Thus, if both copies of the MHC is inherited from the same common ancestor due to inbreeding there is only half the combinations of genetic information to counteract environmental and harmful problems the immune system is geared to combat. Not only does this provide better defense against pathogens, but there is growing evidence that parents who carry different MHC haplotypes may have fewer fertility problems. This is not a universally accepted theory, but today one is hard pressed to find a conservation or zoo biologist concerned with preserving an endangered species who would not list maintaining maximum genetic diversity as one of his/her primary goals. The MHC is very specific and in a way each gene in the MHC helps to create individual one type of cell that is specific to and capable of recognizing and killing only one kind of dangerous environmental problem. Examples of environmental insults includes such things as pollen, dust mite saliva, fly bite, insect venom, cancer cells, viruses, bacteria etc. The environment has billions upon billions of different insults that the animal may encounter in its lifetime and for each insult only one MHC gene will have the ability to counteract the insult. Now consider a very inbred individual that has two copies of same MHC that followed the limits of probability and was passed down from the same ancestor. If both chromosomes of the dog have the identical immune system gene segments, that animal has lost half of its potential antibody genes. If that animal is further inbred, it starts to lose other individual gene segments to a genetic phenomenon we noted in a previous section called "crossover." Ultimately with continued inbreeding depression we may lose billions of potential antibodies. Maybe we lost that antibody that was required to fight that particular cancer our dog died of. Our dogs may also exhibit allergies to common things due to inbreeding depression....to continue reading this article please click on here...
