题目内容
（请给出正确答案）
According to Hahn, all the following increase the transmission of AIDS virus EXCEPT
A．hunting and killing more chimpanzees.
B．more champ hunters moving to cities.
C．people's changed sexual behaviours.
D．travelling to more African countries.
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更多“According to Hahn, all the fol…”相关的问题
According to Hahn, the HIV epidemic originated in
A．Cameroon.
B．Kinshasa and Brazzaville.
C．Congo River.
D．Nile River.
A．hunting and killing more chimpanzees.
B．more champ hunters moving to cities
C．people’s changed sexual behaviors.
D．travelling to more African countries.
According to Scott Hahn, one big challenge to designers who will go organic is that .
A) much more time is needed to finish a dress using sustainable materials .
B) they have to create new brands for clothes made of organic materials .
C) customers have difficulty telling organic from non-organic materials .
D) quality organic replacements for synthetics are not readily available .
Hahn氏切迹什么时候最明显
A、2个月以前的婴儿
B、4个月以前的婴儿
C、6个月以前的婴儿
D、8个月以前的婴儿
E、10个月以前的婴儿
According to a report in the current issue of Nature, a team of scientists based at M. I .T.'s Whitehead Institute for Biomedical Research has finally managed to make human ceils malignant -a feat they accomplished with two different cell types by inserting just three altered genes into their DNA. While these manipulations were done only in lab dishes and won't lead to any immediate treatment, they appear to be a crucial step in understanding the disease. This is a "landmark paper," wrote Jonathan Weitzman and Moshe Yaniv of the Pasteur Institute in Paris, in an accompanying commentary.
The dramatic new result traces back to a breakthrough in 1983, when the Whitehead's Robert Weinberg and colleagues showed that mouse cells would become cancerous when subjected to two altered genes. But when they tried such alterations on human cells, they didn't work. Since then, scientists have learned that mouse cells differ from human cells in an important respect: they have higher levels of an enzyme called telomerase. That enzyme keeps caplike structures called telomeres on the ends of chromosomes from getting shorter with each round of cell division. Such shortening is part of a cell's aging process, and since cancer cells keep dividing forever, the Whitehead group reasoned that making human cells more mouselike might also make them cancerous.
The strategy worked. The scientists took connective-tissue and kidney cells and introduce three altered genes—one that makes cells divide rapidly; another that disables two substances meant to rein in excessive division; and a third that promotes the production of telomerase, which made the cells essentially immortal. They'd created a tumor in a test tube. "Some people believed that telomerase wasn't that important," says the Whitehead's William Hahn, the study's lead author. "This allows us to say with some certainty that it is."
The problem that has been annoying cancer researchers for years is the difficulty in telling ______.
A．how cancer ceils are formed
B．why cancer cells never stop dividing
C．why normal cells can turn into cancer cells
D．how different normal cells are from cancer cells
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