How Does DNA Store Information?

Your DNA is an “instruction book” to build an entire human being. Hence, your DNA contains an amazing amount of information. Since DNA is just made of chemicals, how is your DNA able to store all this information?

Your DNA stores information in the same way that any other book stores information.

Although a book is full of letters, it is not the letters themselves that store information. Instead, it is the ORDER of the letters that stores information. Consider 100 boxes of Alpha-Bit cereal, which is a cereal shaped like letters. Together the boxes would contain many thousands of letters but absolutely no information. But what if you poured out the boxes onto a gymnasium floor, and arranged the letters into words, sentences, and paragraphs? Then you would have a lot of information. By only arranging the letters in ORDER you would go from no information to a lot of information.

In the same way it is not the chemicals in DNA that store information. Instead it is the ORDER of the chemicals that stores information. These chemicals are the letters of the DNA Instruction Book.

The English language uses 26 different letters, but the DNA language uses only four letters1 which are four distinct chemicals.2 As with any book, these four letters are used in various combinations to store information.

DNA stores an amazing amount3 of information in a space the size of a microscopic dot. Packed into this tiny space are billions of letters arranged in a complex order to store all4 the information needed to build a complete human being!

References and Notes for Chapter 6:

1. If it seems strange that DNA uses only four different letters to store information, consider a computer which uses only two letters. The hard drive in a modern computer stores all its information by using trillions of switches that can be only “on” or “off,” hence an alphabet of two letters.

2. The four letters (chemicals) of DNA are named adenine, cytosine, guanine, and thymine. Scientists often abbreviate them as A, C, G, and T. These four chemical letters are used a combined total of six billion times in a person’s DNA “book.” This “book” contains the instructions to build an entire human being. By having billions of letters arranged in order, the DNA book is able to store a massive amount of information and is by far the most complex book in the world.

An adult human has about 30 trillion copies of his/her complete DNA book. Although microscopic in size, each copy contains six billion letters arranged in an order that scientists are still far from completely understanding. As explained below, scientists now realize that a straight line reading of this book does not tell the whole story:

Only about 2% of our DNA codes for genes. Scientists once taught that the remaining 98% of our DNA was useless and was simply leftover dead-ends from our supposed Evolutionary past. They even referred to it as “Junk DNA.” Scientists no longer teach this. Geneticists now believe that much of our non-coding DNA plays an important role in our development and functionality. They have even found evidence that non-coding DNA contains multiple layers of information that utilize some sections several times but in different combinations with other sections. It is somewhat analogous to a Word Search Puzzle which uses the same letters in multiple words depending on whether the letters are read forwards, backwards, diagonally, or upside down.

3. The famous Evolution Scientist Carl Sagan once wrote of the amazing amount of information stored in each living cell:

The information content of a simple cell has been estimated at around 1012 bits, comparable to about a hundred million pages of the Encyclopedia Britannica.”  -Carl Sagan, as quoted in Encyclopedia Britannica: Macropaedia Vol. 10, 1984, p. 894.

Note that Sagan was referring to the information content of a “simple” cell, presumably a bacterial cell. A human cell with a single copy of human DNA contains much more information than a bacterial cell.

Most scientists believe that through a process called cloning, we will eventually be able to duplicate an individual from a single copy of the person’s DNA book. Scientists believe this is possible because they believe that each copy your DNA book contains all the unique instructions needed to build you.

4. To begin building an organism, DNA requires an existing cell (egg) with the molecular “tools” to carry out the instructions.