Our genes, or instructions, are coded on short segments of a long chemical chain called DNA. It is in the center of each cell of our bodies. Think of genes as information bits paired along two spiraling strands of this chemical - like snap-together beads in two long, connected strings of DNA.
Every human has the same number and set of genes, so you might think we would all be exactly the same. But the genes themselves vary a lot or a little, just as people do - and as animals do. That's why we do. For example, everyone has a pair of genes for eye color but one variation instructs the eyes to be blue while other variations order green or brown.
Many of the genes in other animals are similar to those in humans. After all, people and animals, like our dogs, all have to do certain things, like digesting food, so we need a similar gene for that. When we are loyal, frisky and bright-eyed - and tip over garbage cans - maybe it's those shared genes?