A schoolgirl starred in the BBC Christmas Lectures presented by the Royal Institution.
Ines Chung-Halpern, 12, of Putney, attended the filming in December and helped with a demonstration for the show.
The annual lectures, titled Life Fantastic, focused on weird and wonderful creatures, with Dr Alison Wollard leading the programme.
Dr Wollard, a genetics lecturer at the University of Oxford, used developmental biology to explore how we can learn about ourselves from different animals.
Ines appeared on stage to demonstrate the percentage of genes we share with animals.
She guessed what percentage of genes we share with rats, cavefish and chimps.
Ines said: "I thought it was amazing – I found it all really interesting which surprised me because usually when you think of a lecture you think it’s going to be really boring.
"In the game it was easy to pick the right answer for the chimp because they’re so similar to us, but it was much harder for the fish and the rat."
Dr Wollard said: "Through Life Fantastic, I want to get people thinking about how one tiny cell is the building block for an entire organism and to understand the incredible potential this concept holds for future medical discoveries that could completely change how we recognise, treat and prevent hundreds of different diseases."
The lecture was screened on December 29 on BBC Four.