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Evolution

10 11 Chromosomes genes and DNA Towards the end of the 19th century, scientists began turning their microscopes on cell nuclei, looking for the components responsible for the evolutionary mechanism, and coining the term chromosome for the stripy pillules they could see in the nucleus. Observations of cell division mitosis, gamete production meiosis and fertilization showed that chromosomes behaved in an organised way and it was soon suggested that they might carry inherited information as strings of heredity particles. By the 1920s the black string inside chromosomes was revealed to be chains of basesugarphosphate nucleotides, deoxyribonucleic acid, or DNA. Its extraordinary doublehelix structure was finally discovered in 1953. DNA is a 4letter code for life, universal to all life on Earth, i.e., all organisms use it in exactly the same way. The number of chromosomes varies from species to species see opposite top, but all animals carry two versions of each chromosome in every cell nucleus, one from Mom, one from Dad, and spaced out along every chromosome are special sections of DNA called genes. the golden section in the pentagram Above Chromosomes live in the nucleus and are made of DNA. The double helix structure, like a twisted ladder, is comprised of pairs of just four bases, adenine A always bonding with thymine T, and guanine G with cytosine C. DNA thus stores information in a doublebinary or quadrinary fashion, with each of the two strands being an identical copy of the other. A few thousand genes are spaced out along each chromosome, with long sections of repetitive noncoding DNA creating space between them. Above Chromosome numbers in certain animals and plants. All animals are diploid, which is to say they carry two copies of each chromosome in every cell nucleus. For example, bats have paternal and maternal copies of 22 chromosomes, so 44 in each cell. Plants can be polyploid, having more than two copies, so triploid three copies, normally infertile crossbreeds, tetraploid four copies, or, even, hexaploid. ANIMALS 3 Mosquito 6 4 Drosophila 8 6 House Fly 12 12 Salamander 24 13 Leopard Frog 26 16 Alligator 32 20 Shrew 40 20 Squirrel 40 22 Bat 44 22 Porpoise 44 23 human 46 27 Garden Snail 54 28 Elephant 56 30 Goat 60 32 Armidillo 64 32 Guineau Pig 64 32 Opossum 64 32 Porucpine 64 35 Camel 70 37 Chicken 74 39 Dog 78 41 Turkey 82 66 Kingfisher 132 104 King Crab 208 PLANTS 7 Petunia, x2, 14 7 Pea, x2, 14 7 Lentil, x2, 14 7 Rye, x2, 14 7 Einkorn Wheat, x2, 14 7 Durum Wheat, x4, 28 7 Bread Wheat, x6, 42 8 Alfalfa, x4, 32 9 Lettuce, x2, 18 10 Corn, x2, 20 11 Bean, x2, 22 11 Mungbean, x2, 22 12 Potato, x4, 48 12 Tomato, x2, 24 12 Rice, x2, 24 12 Pepper, x2, 24 14 Apple, x2, 34 14, Bramley Apple, x3, 52 20 Soybean, x2, 40 24 Tobacco, x2, 48 41 Lily, x2, 82 630 Fern, x2, 1260
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