why are prions unique?

Answer 1

Prions are infectious units that have no genetic information. They exist solely as protiens. All other replicating organisms including viruses use some form of nucleic acid (DNA or RNA) as a genetic basis for replication. Prions do not.

Answer 2

A prion — short for proteinaceous infectious particle that lacks nucleic acid (by analogy to virion) — is a type of infectious agent made only of protein. Prions are believed to infect and propagate by refolding abnormally into a structure which is able to convert normal molecules of the protein into the abnormally structured form, and they are generally quite resistant to denaturation by protease, heat, radiation, and formalin treatments, although potency or infectivity can be reduced. The term does not, however, a priori preclude other mechanisms of transmission.

Answer 3

They are the only non-living infectious particles. Other infections are caused by living bacteria or viruses, but prions are just proteins. Their shape allows them to contact similarly-shaped proteins and turn them into infectious particles as well. They are the cause of a number of diseases, most notably "mad cow disease" and its human analog, "creutzfeld-jacob disease" (CJD).

Answer 4

because they are found in brain tissue and for them to cause disease you have to eat human brain

Answer 5

This is just supplemental information (you got your best answer already), and I supply it cause maybe you didn't know about it. It's pretty interesting:

"Disease could deal a deathblow to Tasmanian devil population

By Sandra Blakeslee
NEW YORK TIMES NEWS SERVICE

June 15, 2005

LAUNCESTON, Tasmania – Even by the brutish standards of Tasmanian devils, Rosie, Harry and Clyde have led a lamentable life.

A year ago, when the three were each the size of a sesame seed, they wriggled out of their mother's birth canal and undulated their way to her pouch. There, each locked onto a teat and grew like gangbusters.

But tragedy struck. Within months, their mother developed devil facial tumor disease – a mysterious malady that in the last three years has killed nearly half of all the world's devils, marsupials that are found only in Tasmania. Shortly after she died, the baby devils, grown to the size of tiny puppies, were found dangling from their mother's pouch, starving to death.

Rescued and reared by hand, Rosie, Harry and Clyde recently joined six similarly orphaned devils at the Launceston Lakes and Wildlife Park, all in strict quarantine. The fate of their exotic species – Sarcophilus harrisii – may lie in what happens to these rambunctious youngsters in the next 12 to 18 months.

"If they contract the disease, devils may be headed for extinction in the wild," said Nick Mooney, a wildlife biologist with Tasmania's Department of Primary Industries, Water and Environment in Hobart. "If they're free of the disease, we may have reason for hope."

Right now, wildlife experts are struggling to comprehend the nature of the fast-moving epidemic. Moving at a rate of six to 10 miles a year, it is 100 percent fatal. Only the west coast, isolated by mountain ranges inhospitable to devils, is disease-free. Nearly half of the estimated 150,000 devils in Tasmania are now dead.

Cleanup crew

Devil facial tumor disease is grotesque; the mother of Rosie and her brothers died when tumors ballooned out of her face and neck, choking off her ability to eat. It is also an extraordinary puzzle. Scientists do not understand its cause, mode of transmission, time from infection until the tumors appear, or potential to infect other species.

Their current best guess breaks all the rules of modern biology. Scientists suspect that the disease is caused by a cancer cell that itself moves from one animal to another when they bite one another.

Having declared an emergency, officials are trapping healthy devils for captive breeding in case the disease cannot be stopped.

Geoff King, who lures devils to his ranch in northwestern Tasmania for ecotourists to observe, said they lived solitary, nocturnal lives, coming together to devour carrion. Their bite is as strong as that of a dog four times their weight. "They are nature's cleanup crew," King said.

Devils got their name from early European settlers who heard spine-chilling screams in the night and thought that Satan was surely in the back yard. "Devils do make weird noises," King said. "When they first arrive at a carcass," he said, "they make a recognition signal – whorf? Are you there? Then they start hissing from the stomach. Growls turn to whines and flow into screeches. They sound like a groaning witch."

Devil sex turns up the volume. In March and April, males engage in vicious, blood-soaked combat, said Dr. Menna Jones, a wildlife biologist who also works in the environment department. Females select "big butch dudes," Jones said, and allow themselves to be dragged by the scruff of the neck into a burrow. There they scream and fight for several days, mating many times for hours at a time. At the end of such bouts, the male thrusts his sperm into the female every two minutes.

Three weeks later, the female gives birth to about 20 or 30 embryos that wiggle through a string of mucus that leads to her pouch, which has only four teats, Jones said. The first to arrive lock on and survive. All others perish.

Cancer connection

Here in Launceston, Dr. Stephen Pyecroft is spearheading the government's investigation into what is causing the disease. But the leading theory is that devil facial tumor disease is caused by a transmissible tumor cell, Pyecroft said. In this hypothesis, tumor cells alone are the infectious agent. In nature, this is not supposed to happen, Pyecroft conceded. Healthy animals exposed to pathogens, including tumor cells, will normally mount an immune response to fight off the infection.

But genetically speaking, devils are virtual clones. With scant variation in their DNA – perhaps from a population bottleneck in the recent past – they may have nearly identical immune systems. Hence they cannot fight off the tumor cells.

Another team is trapping devils islandwide to determine the extent of the epidemic. The team is also in the process of trapping 25 young animals from apparently disease-free areas as an insurance policy. The juvenile devils are being placed in urban and offshore sites to keep them apart from older, wild devils. If after a year or so they show no signs of disease, they will be bred to ensure survival of their species."