I decided to write this blog thanks to a recent blog thought over on CBC’s website. CA authored an article called “Genetic Diseases: Why Inbreeding is Bad” (http://colorblindcupid.wordpress.com/2008/06/17/genetic-diseases-why-inbreeding-is-bad/). After making a few comments about genetic predispositions that some ethnicities seem to be prone to, I got to thinking about how some inbreeding populations have also helped us out.

 

Genetics is a double-edged sword. It allows for those genes best fit to survive and be passed onto the next generation. HOWEVER, it also allows interbred groups to pass on recessive genes and mutations. Those mutations may be good or they may be bad, it is up to the coin toss that genetics does. This led me to thinking about The Plague aka Black Death aka Bubonic Plague. For those of you who do not know what that was, it was a time during the Middle Ages of Europe when a great disease spread thanks to rats and fleas. Basically, rats were infected by the bacteria Yersinia pestis. When fleas bit the rats, they contracted the disease, passing it onto anyone or thing they bit. I have a theory that if you trace your genealogy back to Europe, you probably directly descend from someone of noble/royal birth. Why you ask? Well, fleas do not like the scent of horses. It is common knowledge that people during that age bathed only once or twice a year, making them quite smelly. Those that were around horses in turn would smell like them as well. The ones that could afford stables full of horses had to be wealthy or work for the wealthy, so they were fortunate enough to have a natural flea repellant. Unfortunately, when the plague was contracted in the lungs, called pneumonic plague, it became an aerosol that no one seemed to be immune to. It wiped out at least 2/3 of the population of Europe, but there were survivors. There were some lucky souls who happened to contract the Plague and survive it, and these people passed on their genes to their descendants. It was discovered that the plague might have actually allowed for the inheritance of a GOOD mutation within the population.

 

During the 1980’s, there were many blood transfusions, and most of those were not tested for the HIV virus until it was too late. During the notification to recipients that they had been given contaminated blood, only one recipient tested negative for the HIV virus. For years, the man continued to test negative for the deadly virus. This got geneticists curious. For HIV to invade the cell, it has to fit a lock-and-key mechanism. What this means is that the virus acts like a key that fits a lock (receptor) on the cell. Obviously the receptor is not there for the virus but for some other important function. Unfortunately, the HIV virus fills up those receptors, infesting the cell, spreading its own genes. As it turns out, genes come in pairs, and apparently, the man that received the transfusion lacked both copies of the gene that produced these receptors. Therefore, geneticists started tracing the man’s ancestry along with others, trying to determine just WHERE this genetic mutation first appeared. They decided to run a DNA analysis once the technology was available a few years back. They determined he was of European descent and that he carried a double mutation. The mutation was because he inherited a mutated copy of the gene from each of his parents. This got genecists to searching for a time period where someone’s genes could have allowed for such mutations among people of certain populations. They searched the outbreaks of diseases and traced the mutation back to the Great Plague that happened in Europe during the Middle Ages  (http://www.pbs.org/wnet/secrets/previous_seasons/case_plague/clues.html).

 

The geneticists discovered that people of English, Scandinavian, and Germanic heritage seemed to have higher frequencies of this genetic mutation. They then decided to test the blood of a population that had not changed much in the last 500 years, so they tested that of an isolated village in England. Most of the people were the same descendants of people who had lived there hundreds of years ago. Through much DNA analysis, they discovered that almost everyone living in that village was RELATED, and had a common ancestor. This ancestor happened to have a history recorded because she SURVIVED the Black Death. She then passed her genetic mutation onto her descendants, and so on down the line. Those descendants that received TWO copies of the gene mutation are simply IMMUNE or RESISTANT to the HIV virus. Therefore, those that actually survived the plague due to mutation passed on a gene that allows for immunity to the horrible HIV virus (http://www.darwinawards.com/science/bubonic.html) along with immunity/resistance to the Bubonic Plague.

 

Thanks to this great discovery, scientists are testing use of drug analogs to treat HIV and AIDS. An analog basically is a mimic. In this case, it blocks up all the specific receptors that HIV can fit into or causes a change in the cell, mimicking the double genetic mutation. So far, the clinical human trials have been successful. Those that actually HAD full-blown AIDS tested negative to the entire HIV virus after therapy using these new drugs. This could be the breakthrough that the world has been waiting for…all simply to an inbreeding population that passed on a good gene mutation.