雅思阅读 012 · CRISPR: Editing the Book of Life

科技/生物主题。题型：选择题 + T/F/NG。难度：较难（P3）。

🎧 课文朗读音频（约 1 分钟）

正文 Passage

Every living thing carries a set of instructions written in DNA — the double helix discovered by Watson and Crick in 1953. For half a century, reading DNA was hard enough. Changing it was harder still. Then, in 2012, a technology called CRISPR-Cas9 arrived, and everything changed.

CRISPR is a system borrowed from bacteria. For billions of years, bacteria have used it to cut up the DNA of invading viruses. Researchers realised that they could hijack this system, using a guide molecule to point the Cas9 "scissors" at any chosen gene. The result is a cheap, precise and remarkably easy way to edit DNA — in plants, in animals, and, controversially, in human embryos.

The potential benefits are enormous. Genetic diseases that run in families — sickle-cell anaemia, cystic fibrosis, Huntington's — could be eliminated at the source. Crops could be engineered to resist drought and disease, reducing the need for pesticides. Mosquitoes could be modified to stop carrying malaria, saving hundreds of thousands of lives each year.

But the ethical questions are equally enormous. Editing the DNA of an adult patient affects only that person. Editing an embryo, by contrast, changes every cell in the future person's body — and, crucially, changes the DNA they will pass on to their own children. This is "germline editing", and it crosses a line that most scientists have, until recently, agreed not to cross.

In 2018, a Chinese researcher announced that he had used CRISPR to edit the embryos of twin girls, making them resistant to HIV. The announcement was met with near-universal condemnation. The experiment was unnecessary — there are safer ways to prevent HIV transmission — and the long-term effects of the edits are unknown. The researcher was jailed.

The debate, however, has not gone away. As the technology improves, the case for allowing some forms of germline editing — for instance, to prevent severe genetic diseases for which no other treatment exists — will become harder to refuse. The question is no longer whether we can edit the book of life. It is who gets to decide which pages to rewrite, and whether we are wise enough to do it.

题目 Questions

Questions 1-3: Choose the correct letter.

1. What is CRISPR?

• A. a type of virus
• B. a gene-editing system borrowed from bacteria
• C. a new kind of microscope
• D. a genetic disease

2. Why is editing embryos controversial?

• A. it is too expensive
• B. it changes DNA that will be passed to future generations
• C. it only affects the patient
• D. it does not work

3. What happened in 2018?

• A. CRISPR was invented
• B. a Chinese researcher edited human embryos
• C. genetic diseases were cured
• D. all countries banned CRISPR

Questions 4-7: T/F/NG

4. CRISPR makes gene editing cheaper and easier.

5. Editing an adult patient changes their children's DNA.

6. The Chinese researcher who edited twins was praised by the scientific community.

7. No genetic diseases can be treated with CRISPR today.

Questions 8-10: Complete the notes. NO MORE THAN TWO WORDS.

• The Cas9 enzyme acts like molecular (8) ____________.
• Changes made to an embryo affect every (9) ____________ in the future person's body.
• The debate is no longer whether we can edit DNA, but who gets to (10) ____________.

答案 Answers

核心词汇

CRISPR / DNA / gene / embryo / germline / edit / bacteria / virus / sickle-cell / cystic fibrosis / malaria / ethical / condemnation / guideline