DNA is a nucleic acid that contains genetic information used in the development and functioning of living organisms. The purpose of DNA molecules is to store information. DNA is like a set of blueprints, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The segments that carry this genetic information are called genes, but other DNA sequences have structural purposes. They are involved in regulating the use of this genetic information.

DNA is a long polymer of simple units called nucleotides, with a backbone made of sugars and phosphate atoms joined by ester bonds. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription. Most of these RNA molecules are used to synthesize proteins, but others are used directly in structures such as ribosomes and spliceosomes.

Within cells, DNA is organized into structures called chromosomes and the set of chromosomes within a cell make up a genome. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms such as animals, plants, and fungi store their DNA inside the cell nucleus, while in prokaryotes such as bacteria it is found in the cell's cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA, which helps control its interactions with other proteins and thereby control which genes are transcribed.

DNA is the molecule that contains our hereditary information: the instruction book for a person, a bug, a camel or a koala bear.

Here are some interesting DNA science facts:

A list of the bases of the entire DNA in your gene is about 3 billion letters.

In 1985, when the Human Genome Project was first proposed, many critics thought it was absurd. At the time, the technology did not even exist to decode the sequence of a simple bacterium, much less a human being.

While the number of base pairs--3.2 billion--on each unique person's 23 chromosomes is quite impressive, the average human being has a mere 31,000 genes. That's about a third fewer genes than anyone expected and not even double the amount of genes a roundworm has. A variety of amoeba has nearly 200 times as many genes as humans do.

Any two unrelated strangers anywhere on the planet share 99.9 percent of the same DNA. A miniscule fraction of the genome--about 3 million of its over 3 billion bases--accounts for the vast differences within the human race.

Genetically speaking, all races are equal. In other words, you cannot tell someone's race simply by looking at their DNA.

Human beings have roughly 99.1 percent of our genes in common with the chimpanzee, our closest relative on earth. The overlap between mice and humans is surprisingly close, too. We have nearly 75 percent of our genes in common.

Single gene errors account for more than 4,000 known heredity diseases, and the list is growing rapidly. A person's risk for diseases from cystic fibrosis to Huntington's now can be determined by looking at the DNA.

Scientists still don't know what more than 50 percent of genes do. Also a lot of the DNA in our cells is "junk," that is, scientists don't know exactly what the long stretches of repetitive DNA (usually long stretches of Gs and Cs) in our cells are for.

On human chromosome 14, a gene called TEP1 codes for a protein that forms part of a chemical known as telomerase. Some cells turn immortal if you give them enough telomerase. That sounds good, but a cell line known as cancer also needs telomerase for its own immortality project.

For centuries folklore had it that heredity passed through the blood. Think of the terms "bad blood," "mixed blood," "royal blood," "blue blood," or "bloodline." The irony is that there is no heredity coded in your red blood whatsoever. The red blood cells are the only kind of cells in your body that don't have DNA because they're the only cells in your body that don't have nuclei.

DNA has played an important part in solving some of life's big mysteries. Here are some problems that were solved by DNA. See how you can use this information to devise a DNA project your next science fair project.

Many locations, especially in Europe boast that "Columbus is buried here." DNA testing determined which one was correct.

DNA testing has solved many crimes and cleared many people wrongly accused of crimes before genetic testing was available.

The DNA from nearly 1,000 pet cats looks like the DNA of a subspecies of wildcats from the Near East. That zeroes in on the Near East as the place where wild cats first became pets

What burning question can DNA solve for you? A little research into DNA and possible science experiments that you can conduct make excellent material for great science fair projects!

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About the Author

Mort Barish is co-founder of Terimore Institute, Inc. Terimore provides hundreds of science fair projects with step-by-step guides for children in grades K-12 to help them learn more about science. Find fun, easy and award-winning science experiments at www.terimore.com!