When I was researching last month's post on naked mole-rats, I learned that their colonies are inbred: as the National Zoo's article puts it, "because only a few members of the colony produce all the young, and the queen typically mates with close relatives selected from within the colony, naked mole-rat colonies are highly inbred." This made me think about inbreeding depression, a subject which has intrigued me for awhile (you all know I think about some freaky shit). So why don't we explore inbreeding depression and its effect on animals a bit before we go off in search of examples of human beings messed up by inbreeding.
(1) the more closely related two individuals are, the more likely it is that they are both carriers of the same recessive deleterious or lethal gene, which means that if they mate their offspring may be born with the undesirable genetic condition. All human have a number of these recessive genes which are either inherited from a parent or produced by mutation, but the occurrence of each of these variants in the global population is rare. Thus, the chances of non-related individuals both being carriers of the same "bad gene" are small, and since the trait is recessive you're OK as long as you have one good copy, but when related individuals mate the chances increase that they might both have bad copies of the same gene to pass on to their children.
Inbreeding depression can also be a problem for purebred dogs and cats where, for example, physical traits which are prized as being characteristic of the breed can be exaggerated to the point of becoming deformities. An example of this is overly purebred Persian cats whose faces are so flat that they are prone to tear duct overflow, breathing and sinus problems. And as a result of inbred stock, purebred German shepherds often suffer from hip dysplasia which can cause arthritis and lameness.
NEXT TIME: Our search continues with Inbred Royals.
Images: Photo of white lab mice by flickr user Rick Eh? used under Creative Common non-commercial license; photo of Persian cat found on cat chitchat from Stockxpert