| DNA is a nucleic acid that contains genetic information | | | | share 99.9 percent of the same DNA. A miniscule |
| used in the development and functioning of living | | | | fraction of the genome--about 3 million of its over 3 |
| organisms. The purpose of DNA molecules is to store | | | | billion bases--accounts for the vast differences within |
| information. DNA is like a set of blueprints, since it | | | | the human race. |
| contains the instructions needed to construct other | | | | Genetically speaking, all races are equal. In other |
| components of cells, such as proteins and RNA | | | | words, you cannot tell someone's race simply by |
| molecules. The segments that carry this genetic | | | | looking at their DNA. |
| information are called genes, but other DNA | | | | Human beings have roughly 99.1 percent of our |
| sequences have structural purposes. They are | | | | genes in common with the chimpanzee, our closest |
| involved in regulating the use of this genetic | | | | relative on earth. The overlap between mice and |
| information. | | | | humans is surprisingly close, too. We have nearly 75 |
| DNA is a long polymer of simple units called | | | | percent of our genes in common. |
| nucleotides, with a backbone made of sugars and | | | | Single gene errors account for more than 4,000 |
| phosphate atoms joined by ester bonds. Attached to | | | | known heredity diseases, and the list is growing |
| each sugar is one of four types of molecules called | | | | rapidly. A person's risk for diseases from cystic |
| bases. It is the sequence of these four bases along | | | | fibrosis to Huntington's now can be determined by |
| the backbone that encodes information. This | | | | looking at the DNA. |
| information is read using the genetic code, which | | | | Scientists still don't know what more than 50 percent |
| specifies the sequence of the amino acids within | | | | of genes do. Also a lot of the DNA in our cells is |
| proteins. The code is read by copying stretches of | | | | "junk," that is, scientists don't know exactly what the |
| DNA into the related nucleic acid RNA, in a process | | | | long stretches of repetitive DNA (usually long |
| called transcription. Most of these RNA molecules are | | | | stretches of Gs and Cs) in our cells are for. |
| used to synthesize proteins, but others are used | | | | On human chromosome 14, a gene called TEP1 codes |
| directly in structures such as ribosomes and | | | | for a protein that forms part of a chemical known as |
| spliceosomes. | | | | telomerase. Some cells turn immortal if you give them |
| Within cells, DNA is organized into structures called | | | | enough telomerase. That sounds good, but a cell line |
| chromosomes and the set of chromosomes within a | | | | known as cancer also needs telomerase for its own |
| cell make up a genome. These chromosomes are | | | | immortality project. |
| duplicated before cells divide, in a process called DNA | | | | For centuries folklore had it that heredity passed |
| replication. Eukaryotic organisms such as animals, | | | | through the blood. Think of the terms "bad blood," |
| plants, and fungi store their DNA inside the cell | | | | "mixed blood," "royal blood," "blue blood," or |
| nucleus, while in prokaryotes such as bacteria it is | | | | "bloodline." The irony is that there is no heredity |
| found in the cell's cytoplasm. Within the | | | | coded in your red blood whatsoever. The red blood |
| chromosomes, chromatin proteins such as histones | | | | cells are the only kind of cells in your body that don't |
| compact and organize DNA, which helps control its | | | | have DNA because they're the only cells in your body |
| interactions with other proteins and thereby control | | | | that don't have nuclei. |
| which genes are transcribed. | | | | DNA has played an important part in solving some of |
| DNA is the molecule that contains our hereditary | | | | life's big mysteries. Here are some problems that |
| information: the instruction book for a person, a bug, | | | | were solved by DNA. See how you can use this |
| a camel or a koala bear. | | | | information to devise a DNA project your next |
| Here are some interesting DNA science facts: | | | | science fair project. |
| A list of the bases of the entire DNA in your gene is | | | | Many locations, especially in Europe boast that |
| about 3 billion letters. | | | | "Columbus is buried here." DNA testing determined |
| In 1985, when the Human Genome Project was first | | | | which one was correct. |
| proposed, many critics thought it was absurd. At the | | | | DNA testing has solved many crimes and cleared |
| time, the technology did not even exist to decode | | | | many people wrongly accused of crimes before |
| the sequence of a simple bacterium, much less a | | | | genetic testing was available. |
| human being. | | | | The DNA from nearly 1,000 pet cats looks like the |
| While the number of base pairs--3.2 billion--on each | | | | DNA of a subspecies of wildcats from the Near East. |
| unique person's 23 chromosomes is quite impressive, | | | | That zeroes in on the Near East as the place where |
| the average human being has a mere 31,000 genes. | | | | wild cats first became pets |
| That's about a third fewer genes than anyone | | | | What burning question can DNA solve for you? A |
| expected and not even double the amount of genes | | | | little research into DNA and possible science |
| a roundworm has. A variety of amoeba has nearly | | | | experiments that you can conduct make excellent |
| 200 times as many genes as humans do. | | | | material for great science fair projects! |
| Any two unrelated strangers anywhere on the planet | | | | |