This outta make the fundie heads explode: evolving pathogens, mutant genes and immunity to AIDS:popcorn:
Did a genetic mutation save the English village of Eyam from the Great Plague? The Mystery of the Black Death begins in September of 1665, when a tailor in the secluded English village of Eyam opened a flea-infested shipment of fabric from London. In a matter of days, the tailor and much of the village were suffering the telltale signs of bubonic plague, the disease that, in the first five years since its arrival, had wiped out a third of the European population. To prevent the outbreak from spreading throughout the region, the whole town was quarantined -- no one was allowed in or out. Outsiders assumed that the bacteria would simply wipe out the entire village. But they were wrong. Three hundred and fifty years later, Dr. Stephen O'Brien, a geneticist from the National Institutes of Health in Washington, D.C., is delving into the reasons why some individuals managed to survive the excruciating Black Death while others were dying all around them. Following O'Brien as he takes DNA samples and investigates historical records and family archives, the film sheds light on the resistance to the plague, and reveals a stunning legacy that the plague survivors passed on to their descendents -- a similar resistance to the modern-day scourge of AIDS.
SECRETS OF THE DEAD: Crime Scene Investigations Meet History
DNA samples could only be collected from direct descendents of the plague survivors. DNA is the principal component of chromosomes, which carry the genes that transmit hereditary characteristics. We inherit our DNA from our parents, thus Eyam resident Joan Plant, for instance, may have inherited the delta 32 mutation from one of her ancient relatives. Plant can trace her mother's lineage back ten generations to the Blackwell siblings, Francis and Margaret, who both lived through the plague to the turn of the 18th century. The next step was to harvest a DNA sample from Joan and the other descendants. DNA is found in the nuclei of cells. The amount is constant in all typical cells, regardless of the size or function of that cell. One of the easiest methods of obtaining a DNA tissue sample is to take a cheek, or buccal, swab.
After three weeks of testing at University College in London, delta 32 had been found in 14% of the samples. This is a genetically significant percentage, yet what, really, did it mean? Could the villagers have inherited delta 32 from elsewhere, residents who had moved to the community in the 350 years since the plague? Was this really a higher percentage than anywhere else? To find out, O'Brien assembled an international team of scientists to test for the presence of delta 32 around the world. "Native Africans did not have delta 32 at all," O'Brien says, "and when we looked at East Asians and Indians, they were also flat zero." In fact, the levels of delta 32 found in Eyam were only matched in regions of Europe that had been affected by the plague and in America, which was, for the most part, settled by European plague survivors and their descendents.
Meanwhile, recent work with another disease strikingly similar to the plague, AIDS, suggests O'Brien was on the right track.
HIV, the virus that causes AIDS, tricks the immune system in a similar manner as the plague bacterium, targeting and taking over white blood cells. Virologist Dr. Bill Paxton at the Aaron Diamond AIDS Research Center in New York City noticed, "the center had no study of people who were exposed to HIV but who had remained negative."
He began testing the blood of high-risk, HIV-negative individuals like Steve Crohn, exposing their blood to three thousand times the amount of HIV normally needed to infect a cell. Steve's blood never became infected. "We thought maybe we had infected the culture with bacteria or whatever," says Paxton. "So we went back to Steve. But it was the same result. We went back again and again. Same result." Paxton began studying Crohn's DNA, and concluded there was some sort of blocking mechanism preventing the virus from binding to his cells.
Further research showed that that mechanism was delta 32.http://www.pbs.org/wnet/secrets/case_plague/index.html
Printer-friendly format
Email this thread to a friend
Bookmark this thread
(1000+ posts)
Send PM |
Profile |
Ignore
