Gene Editing C1 Lesson: Therapies, Embryos, and Ethics

Level: C1

Printable: Student handout (PDF) | Teacher’s key (PDF)

Reading

Genetic engineering in humans falls into two different categories. Somatic editing changes cells in one person, usually after birth, and the change is not passed on. Germline editing changes embryos, eggs, or sperm, so the change is heritable and would appear in every later generation. Many scientific societies that call for caution on germline editing support somatic therapies. Because forecasts about a young technology are easily wrong, this reading separates what has happened from what is only likely.

The first CRISPR therapy to reach patients was Casgevy, approved in the United Kingdom and the United States in late 2023 for sickle cell disease. It works by editing a patient’s blood stem cells outside the body and returning them. Its US list price was $2.2 million, and in July 2026 the FDA extended its use to children aged two and older. Yet a 2023 Global Burden of Disease study in The Lancet Haematology estimated that about 7.7 million people were living with the disease in 2021, most of them in sub-Saharan Africa, so access is a central question.

A second development is the bespoke therapy. In 2025, doctors at Children’s Hospital of Philadelphia treated an infant, known as Baby KJ, who had a liver disorder called CPS1 deficiency. They built a base editor, a tool that changes a single DNA letter, for his single mutation and delivered it to his liver inside tiny fat particles. It took about six months to build. The treating team reported early improvements. It remains a single patient, however, and only long-term follow-up can show whether the benefit lasts.

The regulatory pathway is changing to fit such cases. In November 2025, FDA leaders proposed a “plausible mechanism” route in the New England Journal of Medicine, and draft guidance followed in February 2026. The framework requires that the disease have a known biological cause and that the treatment target it directly, and it asks that each developer monitor patients’ safety closely after approval. The Philadelphia team argues that positive results in as few as five to ten patients might support approval of a whole platform of related editors. Ethicists have warned that the pathway could be stretched too far. Economics may decide the outcome: a treatment for a few patients must become scalable and equitable to matter widely.

Before birth, the nearest technology is not editing but screening. Polygenic embryo screening adds up thousands of small genetic differences to rank embryos from in vitro fertilization (IVF) by estimated disease risk or, with some providers, traits. Genomic Prediction, a US company, launched it commercially in 2019, and another provider, Orchid, charges $2,500 per embryo on top of the cost of IVF. Its predictive value is disputed. In a 2024 simulation using data from BioBank Japan, University of Tokyo researchers found that different scoring methods often disagreed about which embryo was “best”, so the rankings were not robust. The European Society of Human Genetics called the practice unproven and unethical in 2021 and recommended that patients be told of its limits and that a public debate take place before wider use. Because screening does not alter DNA, it faces fewer legal barriers and may spread faster than editing.

Editing embryos is far more contentious. In 2018, the Chinese scientist He Jiankui announced the birth of twin girls from edited embryos. The international summit in London in 2023 concluded that heritable editing remains unacceptable and that safety and efficacy must first be established, and in 2025 several societies urged that heritable editing be paused for ten years. A 2020 survey in The CRISPR Journal found that 75 of 106 countries prohibit it. Technical obstacles remain, notably mosaicism, in which an embryo’s cells are edited unevenly. Money is another: by early 2026, two US start-ups that planned embryo editing had shut down, while a third, Preventive, said it would not attempt a pregnancy unless safety could be shown. A 2025 analysis in Nature suggested that editing many variants at once could theoretically reduce disease risk sharply, but it treated such editing as feasible only over the next few decades.

Several outcomes seem likely over the next decade, although none is certain. Personalized somatic therapies will probably grow, limited by manufacturing and cost, and screening will probably expand faster than editing. Heritable editing is likely to stay outside clinical practice while its safety is unproven, partly because its effects would be irreversible across generations. The prospect of enhancement, editing healthy embryos for traits such as height, has a few proponents, who argue that parents should be free to choose, and many critics, who fear new inequality. Legal safeguards also differ widely between countries. The largest uncertainties are therefore social as much as scientific. The next concrete test is whether the first platform approvals under the new FDA pathway arrive, and at what price.

Vocabulary

Each word has a frequency score, a rank, and a tag. The score shows how common the word is in modern English: higher means more common, and each full point means roughly ten times more common. The rank is the word’s position on a list of about 321,000 English word forms, from most to least common. The tag shows where you are most likely to meet the word: Current, Formal, Literary, or Dated. The paragraph number shows where the word first appears in the reading. The labels are information, not instructions. Deciding which words are worth your time is up to you. How to read the scores, ranks, and tags.

Germline editing is heritable, so changes pass to later generations.
Eye color is a heritable trait.

A second development is the bespoke therapy.
He wore a bespoke suit.

The regulatory pathway is changing to fit such cases.
The new pathway could speed up approval.

A treatment must become scalable to reach many patients.
The software is scalable for large companies.

A treatment must become equitable to matter.
The city wants an equitable share of the funds.

Different scoring methods often disagreed, so the rankings were not robust.
The team repeated the test with new data, and the results were robust.

Editing embryos is far more contentious.
The proposal was a contentious issue in parliament.

Mosaicism means an embryo’s cells are edited unevenly.
Embryo editing is harder to check because of mosaicism.

Editing many variants could theoretically reduce disease risk sharply.
Theoretically, the plan should work, but nobody has tried it.

It treated such editing as feasible only over decades.
Is the plan technically feasible?

Heritable editing is irreversible across generations.
The damage to the forest was irreversible.

The prospect of enhancement divides opinion.
There is little prospect of a quick agreement.

The prospect of enhancement divides opinion.
Performance enhancement is banned in sport.

Enhancement has a few proponents, who argue that parents should be free to choose.
Proponents of the plan say it will save money.

Safeguards differ widely between countries.
The law includes safeguards for patients.

Activity Page

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Speed Challenge

Answer 12 questions against the clock. Every wrong answer adds 5 seconds, and the lowest score wins. Open the speed challenge in a new tab.

Shadow Reading and Typing: The Debate I Did Not Win

This short text uses many of the words from this lesson. Use it for shadow reading (reading aloud along with a model) and for typing practice.

Last semester, I chose genetic engineering for a class debate, assuming it would be simple to argue. It was not. I quickly learned that editing a patient’s own cells is very different from editing embryos. In an embryo, the change would be heritable and passed on to future generations.

The medical side impressed me. One infant received a bespoke therapy built for his single mutation. Regulators are now designing a new pathway for treatments like his. Still, a therapy for one child only matters widely if it becomes scalable. With some treatments costing millions of dollars, I kept asking whether access could ever be equitable.

Embryo screening turned out to be more contentious than I expected. Companies rank embryos by estimated risk, but one study found that the rankings were not robust. Editing embryos raises even harder problems. Scientists still struggle with mosaicism, in which cells are edited unevenly. Many edits might theoretically lower disease risk, but few think this is feasible soon.

In the end, what worried me most was that such changes would be irreversible. My opponents raised the prospect of enhancement, and its proponents argue that parents should be free to choose. I argued that legal safeguards differ too much between countries for anyone to move quickly. Neither side won, but I left the debate far less certain than I arrived.

How to practice

Read the text silently once and check any words you are unsure of.
Read it aloud slowly, one sentence at a time. On the typing page, the Listen button reads each line with your device’s voice, so you can listen first and then repeat.
Shadow: read aloud again at a natural speed, trying to keep a steady rhythm without stopping.
Record yourself, listen back, and note one sentence to practice again.
Type it on the typing page below and check your speed and accuracy.

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Comprehension Questions

Explain the difference between somatic and germline editing and why the reading organizes its argument around it.
What do Casgevy and its price show about the promise and the limits of gene editing?
Describe Baby KJ’s treatment. Why does the reading call it bespoke, and what caution does it add?
How would the plausible mechanism pathway change approval, and what do ethicists warn?
What is polygenic embryo screening, and why does the reading say it may spread faster than editing?
Summarize the state of heritable embryo editing: the events, the positions of scientific bodies, and the technical problems.
The reading uses words such as theoretically, probably, and is likely to. What do they show about the strength of the evidence?
Which of the outcomes in the last paragraph seems most likely, and which least certain? Explain.
Evaluate the sources (journal reports, regulators, professional societies, journalists, companies). Which claims are best supported?

IELTS-Style Questions

True, False, or Not Given: “Orchid offers its embryo screening in Japan.” Explain your answer using evidence from the reading.
Yes, No, or Not Given: “The writer believes that forecasts about gene editing should be treated with caution.” Explain your answer using evidence from the reading.
Author’s purpose: Why does the writer treat therapy after birth before editing before birth? What effect does this order have?

AI Discussion Prompt

I just read a C1 English lesson called Genetic Engineering: What Comes Next, Before and After Birth. It covered somatic and germline editing, Casgevy and its cost, Baby KJ’s personalized therapy, the FDA plausible mechanism pathway, polygenic embryo screening, the debate and moratorium on heritable embryo editing, and the likely outcomes over the next decade. I am an advanced English learner at about C1 level. Please have a balanced conversation with me about the benefits, risks, and ethics of gene editing, presenting more than one perspective and not telling me what to conclude. Do not ask about my own health or genetic conditions. Ask one question at a time. Encourage me to use words like heritable, bespoke, pathway, contentious, and safeguards. Respond to my ideas first, then briefly point out one or two language errors or more precise word choices.

AI Vocabulary Prompt

I want to practice vocabulary from a lesson about the future of genetic engineering. Please quiz me on the following words one at a time, using a mix of question types: multiple choice, true/false, and sentence completion. Give me feedback after each answer before moving on, and bring back the words I miss later. Here are the words: heritable, bespoke, pathway, scalable, equitable, robust, contentious, mosaicism, theoretically, feasible, irreversible, prospect, enhancement, proponents, safeguards.

Discussion Questions

The reading separates somatic and germline editing. Is this distinction clear and stable, or could it blur in the future?
Casgevy costs $2.2 million and most sickle cell patients live in Africa. Who should pay for such therapies, and how should countries prioritize?
Baby KJ’s therapy was designed for one patient. When is it right to develop a treatment for a single person?
The plausible mechanism pathway could approve a platform on results from five to ten patients. What are the benefits and risks of a lower evidence bar?
Polygenic embryo screening ranks embryos by predicted risk or traits. Where should the line be between preventing disease and choosing traits?
Researchers in Tokyo found that different scoring methods often disagreed about the best embryo. Should a test with such uncertain results be sold to parents?
The London summit said heritable editing remains unacceptable at this time. What evidence and discussion would be needed to change that view?
A 2020 survey found that 75 of 106 countries prohibit heritable editing. How could such rules be enforced if a company moved its work to a country without them?
Mosaicism is a technical obstacle to embryo editing. How should scientists and the public treat a promised technology with unsolved technical problems?
Proponents of enhancement stress parents’ freedom to choose, while critics fear inequality. Which argument do you find stronger, and why?
Editing that is heritable is irreversible across generations. Does irreversibility justify a stricter standard of proof than for somatic therapy?
Should the public decide questions such as enhancement, or should experts? What role should each have?
How should journalists describe forecasts about gene editing in a way that separates evidence from hope?
Which single safeguard would you most want in place before any heritable editing is tried, and why?

Language Focus: The Mandative Subjunctive: Require That, Urge That

What it is: After verbs and nouns of demand, recommendation, or proposal (urge, require, insist, recommend, propose, request), formal English uses that + subject + base verb, with no -s and no auxiliary: They urged that the trials be paused. It can also be expressed with should (should be paused). The negative puts not before the verb: that the trial not proceed.

Why writers use it: Regulation and ethics texts describe what people want done, not what is done. The mandative structure states a demand or requirement compactly and formally, and it keeps the verb in a neutral form that does not describe a fact.

Examples from the reading:

“The framework requires that the disease have a known biological cause and that the treatment target it directly.”
“…and it asks that each developer monitor patients’ safety closely after approval.”
“…recommended that patients be told of its limits and that a public debate take place before wider use.”
“…in 2025 several societies urged that heritable editing be paused for ten years.”

Practice task: Rewrite with a mandative subjunctive: “The committee requires the company to publish its data.” Begin with The committee requires that…

(Example answer: “The committee requires that the company publish its data.”)

Recommended Resources

FDA Approves First Gene Therapies to Treat Patients with Sickle Cell Disease (US Food and Drug Administration, 2023). The regulator’s announcement of Casgevy, the first CRISPR therapy.
CHOP Marks One-Year Anniversary of the World’s First Personalized CRISPR Gene Therapy (Children’s Hospital of Philadelphia, 2026). An account from the treating hospital, including the plausible mechanism pathway.
ESHRE Supports the Position of ESHG on Embryo Selection Based on Polygenic Risk Scores (European Society of Human Reproduction and Embryology). A European fertility society explains why it does not support ranking embryos by polygenic scores.
International Call for a 10-Year Moratorium on Heritable Human Genome Editing (ASGCT and partners, 2025). The statement from scientific societies that draws the somatic and heritable line.
Heritable Polygenic Editing: The Next Frontier in Genomic Medicine? (Visscher et al., Nature, 2025). The analysis of what editing many variants could do in theory.