Question

Elephants have impressed us for centuries. They are big, clever, and sociable. But what if someone told you that they may also hold the key to fighting cancer?

People have been wondering why elephants do not develop cancer, even though they have life spans（寿命）that are similar to humans, living for around 50 to 70 years.

Now scientists believe they know why. A team at the University of Chicago, Us has found that elephants carry a large number of genes that stop tumors（肿瘤）from developing. To be precise, they found 20 copies of an anti-tumor gene called TP 53 in elephants. Most other species, humans included, only carry one copy.

According to the research, which was recently published on the online science network BioRxiv, the extra copies of the gene improved the animal’s sensitivity to DNA damage. This lets the cells（细胞）quickly kill themselves when damaged before they can form deadly tumors.

“An increased risk of developing cancer has stood in the way of the evolution of large body sizes in many animals,” study author Dr Vincent Lynch told The Guardian. If every living cell has the same chance of becoming cancerous, large creatures with long life spans like whales and elephants should have a greater risk of developing cancer than humans and mice do. But across species, the risk of cancer does not show a connection with body mass.

This phenomenon was found by Oxford University scientist Richard Peto in the 1970s and later named “Peto’s paradox”. Evolutionary biologists believe it results from larger animals using protection that many smaller do not, In the elephant’s case, the making of TP53 is nature’s way of keeping this species alive.

The study also found that when the same genes were brought to life in mice, they had the same cancer resistance as elephants. This means researchers could use the discovery to develop new treatments that can help stop cancers from spreading or even developing in the first place.

“Nature has already figured out how to prevent cancer,” said Joshua Schiffman, an oncologist at the School of Medicine, University of Utah, US.

“It’s up to us to learn how different animals tackle（对付）the problem so we can use those strategies to prevent cancer in people.”

1.Why are elephants unlikely to develop cancer?

A. They have a large body size

B. They carry many genes that keep tumors from developing

C. Certain genes in their body kill existing tumors

D. Their genes suffer no DNA damage

2.According to Dr. Vincent Lynch, what has been a risk in the evolution of large animals?

A. Extreme weather             B. Cells killing themselves

C. Human behavior             D. A risk of deadly tumors

3.What does the underlined expression “this phenomenon” on the sixth paragraph refer to?

A. The risk of cancer is not related to body size

B. Larger animals have protection from TP53

C. Larger animals suffer the same risk of cancer as smaller ones do

D. The larger animals are, the bigger risk of cancer they have

4.We can conclude from the last three paragraphs that       .

A. depending on nature is not enough to fight against cancer

B. the TP53 genes have proven useful in stopping cancer in mice

C. this new treatment is more effective than the present ones

D. humans are expected to stop cancer in the near future

Answer

1.B

2.D

3.A

4.B

【解析】

试题分析：本文讲述的是大象为何很少患癌症的原因，这对人类治疗肿瘤具有非常重要的意义。

1.B考查细节理解题。根据文章第三段的A team at the University of Chicago, Us has found that elephants carry a large number of genes that stop tumors（肿瘤）from developing美国芝加哥大学的一个团队发现,大象携带大量的基因,阻止肿瘤(肿瘤)的发展，可知大项不得癌症是因为本身具有的基因问题。故选B项。

2.D 考查细节理解题。根据文章第五段的“If every living cell has the same chance of becoming cancerous, large creatures with long life spans like whales and elephants should have a greater risk of developing cancer than humans and mice do如果每一个活细胞都有相同的机会成为癌变,大型动物寿命长像鲸鱼和大象应该有一个更大的比人类和老鼠患癌症的风险”可知，体型大的动物具有得癌症的更大肿瘤。故选D项。

3.3】A考查细节理解题。根据文章第五段的最后一句话But across species, the risk of cancer does not show a connection with body mass但跨物种,罹患癌症的风险并不与身体质量有关。This phenomenon指的是这种现象。可知A项正确。

4.The study also found that when the same genes were brought to life in mice, they had the same cancer resistance as elephants研究还发现,当相同的基因被带到生活在老鼠身上,他们有抗癌症和大象一样，再根据TP53找到第六段的最后一句话可断定B项是正确的。

考点：社会生活类阅读理解