An Introduction to DNA and Chromosomes
Part 2

A closer look at what makes up the human genome...

Why is DNA so important?

What makes DNA so exciting to scientists is that it shows how living organisms store information in biological molecules. The structure of DNA is nicely suited to such a task. The structural backbone creates a simple, consistent chain upon which many, many bases can be laid out in an orderly, linear sequence. If we think of these four bases – A, T, G, and C – as the “letters” of a genetic “alphabet,” we have the building blocks necessary to encode lots of information within these relatively compact DNA molecules.

DNA therefore shows how living organisms can pass information along to their offspring. DNA tells us how a child can be born with “his mother’s eyes,” for example, or “his father’s nose.” For quite some time, scientists had no viable explanation for this phenomenon. No biological molecule was compact yet complex enough to carry the information needed to guide the development of an entire organism. We now know that when a couple have a baby, the DNA of both parents is the crucial ingredient that is passed on to the child. This amazing molecule is thus responsible for the inherited features of every newborn child.

So how can a DNA molecule ever provide enough information for a living organism? The simple answer is that DNA molecules are very, very long. For example, the DNA molecule of a simple bacteria called E. Coli is four million nucleotides long. In computer terms, this corresponds to the information-storing capacity of an 8 MB hard drive – quite a bit of memory for a small bacteria! The human genome totals approximately 3 billion nucleotides – a 3 GB hard drive! Thus, we can think of DNA as a “genetic database” for organisms.

Last Modified: 9-16-02

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