Shadowing practice: When is editing human DNA okay? | Marvin Liyanage @marvinliyanage

This clip is a fast, evidence driven American lecture from Big Think, and it holds up well for english speaking practice at B2 level. Marvin Liyanage opens with a single scientific result, a human embryo edited with base editing, then moves straight into the ethical questions it raises. The delivery runs at 198 words per minute, faster than 59 percent of the catalogue, so you need to catch each clause before it is gone rather than read it at your own speed.

Across the 21 lines, the talk keeps the same shape an ielts speaking practice answer needs: a claim, evidence for it, then a complication. He states the breakthrough, quotes the risk it creates, then asks who gets to decide, closing on the comparison to Gattaca and a company called Nucleus Genomics. That argument to consequence pattern is exactly what makes it worth repeating out loud, not just reading.

The lines worth studying here are not slang, they are the small grammar moves that keep a spoken argument moving, and getting them right is part of how you improve your english speaking and, eventually, sound less flat in american accent training.

• "Here's why this is such a big deal." The contraction "Here's" carries the stress, and the whole line pivots on it, so the pitch has to drop after "deal" like a door closing on the last point.
• "What if I could choose for my kid to have the protective version of this gene?" A long hypothetical question with no pause markers in the transcript. Say it once for the words, then again for where you naturally need to breathe.
• "That's exactly what Gattica warned us about." "That's" again takes the stress, and "exactly" is the word that needs to land hardest if you want the line to sound like a verdict rather than a fact.
• "The problem is that the same technology that could be used to cure diseases can also be used to make designer babies for rich parents." One long clause with two "could be used to" halves; practising this line is a direct way to work on how to pronounce english words in american accent without slowing the sentence down.

Work the clip in the order the argument builds, not top to bottom by habit. This is what english shadowing practice looks like when the material is a real lecture instead of a dialogue.

• Start with line 1, "Scientists just edited the DNA of a human embryo and it worked," alone, five times, until the stress falls on "edited" and "worked" without you thinking about it.
• Take line 3 next, the 88 percent line, and practise reading the number as part of the sentence rhythm rather than a pause before and after it.
• Move to the run of questions, lines 5, 11, and 14, and read them back to back so you feel the rising pitch pattern repeat three times in a row.
• Finish on line 21, the longest sentence in the clip, and break it at "unless we decide" before attempting it whole; that is the clause most learners rush.
• Once each line is steady on its own, run all 21 in sequence at the clip's own pace, then check your recording against the score rather than your memory of how it felt.