4 Chapter 1 • Genetics and the Organism consecutive nucleotides, which form the “backbone” of the chain. The two intertwined chains are held together by weak bonds between bases on opposite chains (Fig-ure 1-4). There is a “lock-and-key” ±t between the bases on the opposite strands, such that adenine pairs only with thymine and guanine pairs only with cytosine. The Organism (human) A human body is made up of trillions of cells. Each cell nucleus contains an identical complement of chromosomes in two copies. Each copy is a genome. One specific chromosome pair DNA is a double helix. Each chromosome is one long DNA molecule, and genes are functional regions of this DNA. gene gene gene Figure 1-3 Successive enlargements bringing the genetic material of an organism into sharper focus. Figure 1-4 Ribbon representation of the DNA double helix. Blue 5 sugar-phosphate backbone; brown 5 paired bases. bases that form base pairs are said to be
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.