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Each double strand of DNA is coiled into loops, and these are, in turn, coiled into larger super-loops. The super-loops are tightly packed to form an X-shaped body called a chromo- some. Each microscopic cell in the human body contains 46 of these chromosomes.

“o.” There are 37.2 trillion cells in a human body, but a gene section of DNA is even smaller than a cell: to a gene, a cell is like a gigantic “living factory.” Each DNA strand is made up of smaller pieces, or subunits called bases, which are joined together in a long row like beads on a necklace. In the same way that a word carries information by the order of its letters, a DNA carries information by the order of its bases which form a code. We use 26 different letters to make words, but DNA has only 4 different bases: adenine

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Genetic Engineering