All living things are made up of trillions of microscopic units called cells. If we could zoom in on a single, tiny cell, we could see an even teenier “container” inside called a nucleus. It holds a stringy substance called DNA, which is like a set of instructions.
DNA as a set of instructions contains a code for how to build a life-form and consists of features that make an organism unique. Segments, or pieces, of DNA are called “genes”. Humans share 50% of the genes with bananas.
And because all living things on Earth share a common ancestor, the DNA code in different organisms is much more similar than you might expect. Humans, plans and animals share a common ancestor – a single-celled life form which probably lived about 1.6 billion years ago. The genes that we share with many fruits and animals would have been present in that ancestor, and have been passed down to all animals and plants alive today.
In living things, such as us, each gene determines something about our bodies—a trait. In our DNA there are genes that are responsible for hair color, eye color, earlobe shape and so on. We get our DNA from our parents. Some characteristics, like eye color, are pretty much entirely determined by DNA. Some are determined both by DNA and by your environment as you grow up, like how tall you will be as an adult. And some traits are not very directly tied to DNA at all, like the kind of books you like to read. Even identical twins don’t necessarily have identical DNA.
