一本教会你“做对”题的6级阅读书 day14 passage6
Passage 6 Decoding the Tasmanian Devil’s Deadly Cancer
面部肿瘤病威胁“恶魔”生存 《时代周刊》
For such a foul-tempered, fierce and smelly creature,
the Tasmanian devil is beloved in its native Australia,
where it is considered a symbol of the country's frontier toughness.
But as fierce as it is, the devil is in danger of going extinct.
It's not an issue of predators or hunters but of a peculiar,
transmissible disease. Devil facial tumor disease (DFTD)
causes tumors to form in and around the mouth of infected devils;
the tumors eventually grow so large that they prevent the animal
from feeding and lead to starvation. First discovered in 1996,
the cancer has spread swiftly through the Tasmanian devil population,
[01:00]killing more than 70% of the island's animals.
[01:04]If nothing is done to stop the disease,
[01:09]the devils could go extinct within 35 years.
[01:14]But new research on the origins of the fatal cancer suggest
[01:19]that methods for rapid diagnosis and even a vaccine
[01:24]against the disease may be possible.
[01:28]Researchers have identified genetic markers for the disease,
[01:33]which should allow doctors to distinguish facial tumor disease easily
[01:39]from other cancers that afflict the Tasmanian devil, and could eventually
[01:45]help determine a genetic pathway to attack the tumor itself.
[01:52]DFTD is a virtually unique cancer in
[01:57]that it is spread from animal to animal via biting
[02:02]or other physical contact - one of only three cancers
[02:07]that are thought to spread this way.
[02:10]While some human cancers can be linked to transmissible pathogens
[02:16]such as cervical cancer,
[02:18]which is caused by the human papillomavirus in DFTD,
[02:24]infected devils actually transmit the tumor itself
[02:29]to other devils when they bite.
[02:33]Through genetic analysis, the Science team was able to confirm
[02:38]that the tumors being spread from devil to devil
[02:42]were the same genetically identical, exact clonal copies.
[02:48]Using genetic sequencing technology,
[02:52]the team also uncovered the tumors' transmission,
[02:57]which means the set of genes that are activated in tumors.
[03:02]Those activated genes best matched those of Schwann cells,
[03:09]which gave the team a clue as to where the disease originated
[03:14]that's important because devils
[03:17]are unusually amenable to a number of different cancers,
[03:22]and a quick diagnosis
[03:24]before the facial tumors get out of control would be helpful.
[03:30]Better diagnoses may lead to more targeted prevention efforts.
[03:36]Right now the only way to slow the spread of the disease
[03:41]is simply to separate healthy devils from infected ones.
[03:47]Naturalists are creating "devil's islands," cancer-free areas
[03:52]in Tasmania where healthy devils can live and breed.
[03:58]But that alone may not be enough to save the animal.
[04:03]The devils will eventually need a vaccine,
[04:06]and there is hope that this research may help scientists develop one.
[04:12]The team collectioned a catalog of devil genes that affect the tumor
[04:17]and may contribute to its growth;
[04:21]these could be useful targets for designing a future vaccine.
[04:26]The difficulty will be creating a treatment that attacks the tumor,
[04:33]but spares healthy cells. Tough as they are,
[04:37]Tasmanian devils still need a lot of help.