Data shows that 1 in 12 African-Americans carry the sickle cell allele, so any mating between two individuals in this group would increase the probability that their offspring might have the disease. Well-known examples of inherited diseases associated with genetic lineages include Sickle Cell Anemia which is most common in individuals of African ancestry. Since humans tend to marry individuals who are of their same race and religion it means that we are essentially engaged in a limited form of interbreeding. We see examples of this in human populations. Since pedigreed dogs are interbred with other dogs that can trace back to the same ancestry, this clearly predicts that purebreds should be more likely to suffer from inherited diseases than mixed breed dogs. On the other hand, if you have breedings from outside of this lineage (hybrids) the chances are much less. So if you have a line of related individuals that tend to have that allele and they interbreed, the chances that you will get two copies of the defective gene are greatly increased, meaning that many of the offspring will have that genetic disease. (Think of an allele as one of two alternate forms of a gene.) However, in many other instances, we are dealing with a "recessive" disease which will only appear if you get two of the defective alleles (one from the father and one from the mother). For certain genetically caused diseases, all you need is one defective allele in order for the disease to show up. The genetics behind this are really quite simple. Source: Photo by Pets Adviser from Brooklyn, USA Creative Commons Attribution 2.0 Licenseįor as long as I remember it has been argued that mixed breed dogs are healthier than purebred dogs because of "hybrid vigor".
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