DNA is a long string of molecules put together to provide the instructions for making an organism, like you. Think of it as a cookbook where your genes are the recipes and your chromosomes are the chapters.
All living things have DNA. This cookbook is written with only four letters: A, C, G and T. Each stands for a different molecule:
- A= adenine
- C= cytosine
- G= guanine
- T= thymine
These molecules are called bases. Certain bases stick together like puzzle pieces forming pairs (A&T and C&G). Our cookbooks are made up of more than 3 billion of these pairs…talk about a complicated jigsaw puzzle!
Of course our cookbook doesn’t have pages. Instead, your cells read long strings of DNA made up of these A, T, C and G’s. These bases are all held in place, and a particular order, by sugar-phosphate molecules.
Because of bases like to pair up like puzzle pieces, your DNA is made up of two strings, one on top of the other. These two strings actually twist, which is why it is called a double helix.
We have two copies of DNA that we inherited from our parents. One copy came from mom and the other from dad. Because we get a set from both parents, our DNA is unique, so no one has the same set of instructions as you (unless you have an identical twin).
We are however very similar to each other (99.5%). We are also pretty similar to other animals. For example, humans are 90% similar to cats, which seems pretty crazy!
Considering how different we look from cats, it really shows how small changes in DNA can make a significant difference. But this is not too surprising since DNA is made from the same molecules whether you are a person, cat, fish, bug, tree...you name it. The cookbooks of all living things are written with the same language, they just have different recipes.