Page 54 - Heavenly Signs III by Mel Gable
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              Deoxyribonucleic acid (DNA) is an informational molecule encoding the genetic instructions used in the
              development and functioning of all known living organisms and many viruses. Along with RNA and proteins,
              DNA is one of the three major macromolecules that are essential for all known forms of life. Genetic
              information is encoded as a sequence of nucleotides. Within cells, DNA is organized into long structures called
              chromosomes. During cell division, these chromosomes are duplicated in the process of DNA replication,
              providing each cell its own complete set of chromosomes. Within the chromosomes, chromatin proteins exist.
              These compact structures guide the interactions between DNA and other proteins, helping control which parts
              of the DNA are transcribed.


              A gene is a sequence of DNA that contains genetic information and can influence the type of an organism.
              Within a gene, the sequence of bases along a DNA strand defines a messenger RNA sequence, which then
              defines one or more protein sequences. The relationship between the nucleotide sequences of genes and the
              amino-acid sequences of proteins is determined by the rules of translation, known collectively as the genetic
              code. Cell division is essential for an organism to grow, but, when a cell divides, it must replicate the DNA in its
              genome so that the two daughter cells have the same genetic information as their parent. The double-stranded
              structure of DNA provides a simple mechanism for DNA replication. Here, the two strands are separated and
              then each strand's complementary DNA sequence is recreated by an enzyme called DNA polymerase. Different
              mechanisms are used to copy the anti-parallel strands of the double helix. In this way, the base on the old strand
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              dictates which base appears on the new strand, and the cell ends up with a perfect copy of its DNA.
                                                                                DNA:  It is one of the three
                                                                                major macromolecules that are
                                                                                essential for all known forms of
                                                                                life. Genetic information is
                                                                                encoded as a sequence of
                                                                                nucleotides (guanine, adenine,
                                                                                thymine, and cytosine)
                                                                                recorded using the letters G, A,
                                                                                T, and C. Most DNA molecules
                                                                                are double-stranded helices,
                                                                                consisting of two long polymers
                                                                                of simple units called
                                                                                nucleotides, molecules with
                                                                                backbones made of alternating
                                                                                sugars, deoxyribose and
                                                                                phosphate groups, with the
                                                                                nucleobases (G, A, T, C)
                                                                                attached to the sugars. DNA is
                                                                                well-suited for biological
                                                                                information storage, since the
                                                                                DNA backbone is resistant to
                                                                                cleavage and the double-
                                                                                stranded structure provides the



                     DNA Double Helix (GNU)                                     molecule with a built-in
                                                                                duplicate of the encoded

                                                                                information.
              79  Alberts, Bruce; Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts and Peter Walters (2002). Molecular Biology of the
              Cell; Fourth Edition. New York and London: Garland Science.
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