How to explain the concept of DNA to an 8 yr old son?  

I was traveling by bus during my holiday abroad, when my son asked me what is a DNA. I tried to explain in simple language what DNA is. I tried to bring up the example that my son has both DNA of his mum and me. He kept asking questions for half an hour, when I got tired of the conversation, I suggested my son to relax and listen to music that the bus driver was putting on his cd. There was the Gnarls Barkley song "Crazy" and I was singing and humming. After a few seconds my son spoke in a loud voice "Dad if you are saying that I am crazy remember that you have half of my DNA".

Have you ever experienced similar episodes with your children?