The story in three lines. Danya's zip shows two halves that only work together. Margit draws one protein chain with an odd oily patch on its outside, in pencil. Kemi's photograph shows two identical chains joined at those patches, with a groove between them that neither has alone.

One thing to do at the table. Find things that only work as a pair: a zip, scissors, a pair of chopsticks, two hands clapping. For each, ask what the pair can do that one half cannot.

The grown-up layer. Many proteins are made of two or more copies of the same chain, and some only work when the copies are together. A prediction from a single chain can miss this, because it was only given one chain. Clues such as an oily patch on the outside can hint at a partner. Modern prediction tools can also be asked to predict how chains fit together, which is one way scientists now check ideas like this.

For the ride home. Ask: what did Margit's pencil patch turn out to be?