Dna test

DNA is a giant molecule, or combination of atoms. It is arranged in two very long chains of units called nucleotides. The units in each str& are linked together like a chain. The two str&s are linked to each other in a way that resembles a ladder. The ladder is twisted into a shape resembling a spiral, or helix. Because there are two str&s in each DNA molecule, it is often referred to as a double helix. The structure of DNA was discovered in 1953 by two English scientists, James D. Watson & Francis Crick. Watson & Crick later received a Nobel prize for their discovery.DNA str&s are very long. If all of the DNA in one human cell were stretched out, it would measure 5 1/2 feet (1.7 meters) long. If all of the DNA molecules inside all of the cells in a human were stretched out & laid end to end, they would reach from the Earth to the moon & back several thous& times.In every living thing all the information about how that organism will look & function is carried in a material called deoxyribonucleic acid, or DNA. In a human body, for instance, DNA tells the body what color the eyes should be & how big the feet will grow. Each different piece of information is carried on a specific segment of the DNA. These segments are called genes.DNA is found in every cell of every living thing on Earth. Within a cell, DNA is organized into dense complexes called chromosomes. Neither the chromosome or DNA is visible to the naked eye. They can only be viewed with the most powerful of microscopes.When DNA is working correctly it keeps the body functioning properly & allows it to reproduce. Mutations of the DNA can cause diseases or other problems. In the late 20th century scientists studying DNA learned how some mutations occur. They also identified the genes in the human body that control certain functions. They hoped to use this knowledge to improve the health of people with particular diseases. Scientists working with plants learned how to alter the genes of some to make the plants more able to resist certain pests. Because each living thing has a unique set of DNA, & because that DNA is in every cell, experts have also been able to use DNA to identify people based on only a small sample of their cells.Just as in any language, knowing the letters of an alphabet is only one part of communication. In order to get a message across, the letters have to be formed into words. The words spelled from the DNA alphabet form a language called the genetic code of life.All of the words in DNA have just three letters. The order of the DNA letters is called a sequence. Each three-letter word is a code that st&s for an amino acid. For example, the letters CCT st& for an amino acid called proline, while GTT represents the amino acid valine.Amino acids are chemical compounds that make up proteins. When the cell needs to make proteins for growth or repair, it sends a signal to the DNA to begin production of the amino acids that will be needed for the proteins. Certain sections of the cell's DNA have the appropriate sequence for the needed amino acids. Thus these sections will then begin the process of amino acid production.It is very important that DNA is good at spelling because just one mistake can cause the wrong amino acid to be manufactured. Some spelling mistakes are not important, while others can be very serious. For example, the DNA code word for the amino acid glutamate is GAG. If the cell makes a spelling mistake & substitutes a T for the A in this word, the result will be the code word GTG. This codes for a different amino acid: valine. When valine is substituted for glutamate in certain genes in humans, the person will develop the disease sickle cell anemia. Spelling errors are one form of a genetic mistake called a mutation.