Jon wants to know, how do the cells in the human body, in all their variety, differ at the genetic level? James Tytko took his query on... Like this podcast? Please help us by <a href="https://www.thenakedscientists.com/donate">supporting the Naked Scientists</a>

Can a dog and a fox produce viable offspring?

Each week we set out to solve one of the world's weirdest, wackiest, funniest and funkiest scientific puzzles. And along with the answer there's a brand new question to think about for next time...