What does DNA do?
-A middle school student from Michigan
May 28, 2004
DNA is information. Think of DNA as a collection of cookbooks that contains all the recipes for making and running living things like worms, plants, birds, and people.
These recipes determine whether you're a man or a woman, give you your eye color, and tell your body to have two arms and legs, instead of branches and leaves, or tentacles. Almost all of the trillions of cells in your body contain a copy of the entire cookbook collection in a smaller compartment inside the cell called the nucleus.
Your DNA is like the cookbooks of your cell.
Let's call each cookbook in the collection a chromosome. Humans have 23 pairs of chromosomes, one from each parent. That's 46 total in each cell. So that would mean each cell has two editions of 23 different cookbooks.
In our example, each recipe in the cookbooks is like a gene. For humans, this cookbook collection would need to contain at least 25,000 recipes! So how does DNA work?
Imagine that you are making some food in the kitchen. Now imagine that you keep all of your cookbooks bolted to a shelf in the living room. (You may think that's a silly idea, but you have to keep in mind that the logic of biology is sometimes hard to understand.)
Okay, so how are you going to make a recipe if you're not in the same room? You go to the living room and copy it down, and then you bring the copy into the kitchen. When you get to the kitchen, you get the ingredients, follow the recipe, and then you have some food!
In this example, the recipe (a gene) is copied. Actually, since there are two of each cookbook (chromosome), the recipe is copied twice, once from each cookbook. Each copy of the recipe (which, in the cell, is another molecule called messenger RNA) is taken from the living room (the nucleus) to the kitchen (the cytoplasm) where the recipe is converted from words into actual food.
In the cell, the finished product of all this effort is called a protein. Besides being in the food we eat, proteins do almost everything in the cell -- they are what the information in DNA is converted into. They produce and are what the cells are made of, they give you energy, digest your food, and just about everything else. Some examples are hormones (like estrogen, testosterone, or steroids), pigments (that give eyes and skin their color), and antibodies (which help your body fight off infections).
So there you have it. DNA's job is to provide the information on how to build and operate an organism. It does this by having its code copied to messenger RNA and then being translated from the messenger RNA into protein. The proteins are the real workhorses; in most cases, proteins that do just about everything the cell needs are end product of all that effort.
By Joylette Portlock, Stanford University