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Focus on DNA

Chart of How DNA Works, click to see full sizeShort for deoxyribonucleic acid. A nucleic acid that is found in all living cells and certain viruses, has a spiral structure resembling a twisted ladder, and forms the main part of chromosomes. DNA contains genes that determine or influence many of an organism’s traits and that are passed on to the next generation when the organism reproduces. When a cell divides, its DNA replicates to produce two exact copies, one for each daughter cell.

One of the wonders of nature is that the complexity and diversity of life can be contained in a molecule with a relatively simple structure. Deoxyribonucleic acid, commonly called DNA, exists in all organisms. In eukaryotes, it is found inside the nucleus of almost every cell. A DNA molecule consists of two long strands of subunits called nucleotides that are linked together in a structure known as a double helix, which resembles a ladder twisted into a spiral. Each rung is made up of two chemical bases that are joined together by hydrogen bonds. There are four kinds of bases in a DNA molecule: cytosine, guanine, adenine, and thymine— C, G, A, and T, for short. Specific sequences of these bases, known as genes, form codes that contain all of an organism’s genetic information. Most of these codes provide instructions for the production of proteins. The codes are “read” by the processes of transcription and translation.

From CREDO DNA in The American Heritage Student Science Dictionary

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