TOEFL >> Reading >> In the reading part of the TOEFL exam, Passages require understanding of rhetorical functions such as cause-effect, compare-contrast and argumentation. Students answer questions about main ideas, details, inferences, essential information, sentence insertion, vocabulary, rhetorical purpose and overall ideas.
TOEFL Reading - Worksheet 23
Read the passage and choose the best answer to each question.
1. According to paragraph 1, all of the following statements are true EXCEPT
- p53 suppresses tumors
- cancer among elephants is common
- elephants have more genes that encode p53 than humans do
2. The word 'rare' in paragraph 1 is closest in meaning to
3. The phrase 'more robust' in paragraph 2 in closest in meaning to
4. According to paragraph 2 why do people with Li-Fraumeni Syndrome have a higher cancer risk
- because they are born with a 90% cancer risk
- because Li-Fraumeni Syndrome is known to cause cancer
- because they only have one copy of p53
5. According to the passage for what reason does the author suggest that elephants should be developing cancer at a higher rate than humans?
- because of their huge size they have many more cells than humans and these cells are all potentially at risk
- because they have less copies of a gene that protects against cancer
- because it has been predicted that elephants should now be extinct as a result of cancer
6. Paragraph 4 supports most closely which of the following statements about how elephant blood cells protect themselves from damage?
- the blood cells replace themselves
- the blood cells stop themselves dividing
- the blood cells destroy themselves
7. The phrase 'logical reasoning' in paragraph 3 is closest in meaning to
- to give sound and logical reasons for an idea
- the process of using a rational, systematic thought process to arrive at a valid conclusion
- to predict what should be occurring based on evidence
8. Which of the sentences below best expresses the essential information in the Paragraph 4 sentence in bold?
- a damaged cell can keep dividing and result in cancer
- a cell that has been destroyed cannot keep dividing
- if a cancer cell 'commits suicide' it can replace itself afresh, not leaving behind a damaged cell
9. The word 'yield' in paragraph 5 is closest in meaning to
Elephants And Cancer
Despite their huge size and having many more cells than humans, cancer among elephants is quite rare, and new research may explain why. It turns out that elephant cells "have 38 additional modified copies (alleles) of a gene that encodes p53, a well-defined tumor suppressor, as compared to humans, who have only two," researchers at the University of Utah said in a study appearing in today's issue of the Journal of the American Medical Association (JAMA).
The report also says elephants also have a "more robust mechanism for killing damaged cells" that could become cancerous. According to the researchers, among isolated elephant cells, damaged and possibly precancerous cells are destroyed at twice the rate of healthy human cells and five times the rate of people who have Li-Fraumeni Syndrome, with only one working copy of p53. People with this syndrome have "more than a 90 percent lifetime cancer risk in children and adults."
Because elephants have more than 100 times the number of cells as people, they would seem to have 100 times more chance of a damaged cell becoming cancerous. But this is not the case.
"By all logical reasoning, elephants should be developing a tremendous amount of cancer, and in fact, should be extinct by now due to such a high risk for cancer," said Joshua Schiffman, paediatric oncologist at the Huntsman Cancer Institute at the University of Utah School of Medicine, and Primary Childrenís Hospital, in a statement. "We think that making more p53 is natureís way of keeping this species alive."In fact, his research indicates that elephants, who live between 50 and 70 years, have a cancer mortality rate of just under five percent, compared to 11 to 25 percent among humans.
To try to figure out p53ís role, Schiffmanís team collaborated with Utahís Hogle Zoo and the Ringling Brothers Center for Elephant Conservation. They took blood from circus elephants that had been retired to the Center and purposely damaged the cell DNA, a step that can lead to cancer. The cells "committed suicide," researchers said. "Itís as if the elephants said, ĎItís so important that we donít get cancer, weíre going to kill this cell and start over fresh,í" says Schiffman. "If you kill the damaged cell, itís gone, and it canít turn into cancer. This may be more effective of an approach to cancer prevention than trying to stop a mutated cell from dividing and not being able to completely repair itself."
Additional studies will be needed to determine whether p53 directly protects elephants from cancer. While the research may, one day, yield new drugs to fight cancer in humans, researchers say it would not come immediately.
Source: VOA News