biology unit 1- variation, reproduction and new technology

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Inheritance

  • nucleus contains chromosomes which home DNA
  • a section of DNA is called a gene
  • in a nucleus of a sex cell (GAMETE) there is only 1 set of chrmosomes XY, XX, YY
  • in sexual reproduction the child gets two sets of genes, one from father one from mother- resulting in varitation of inherited genes
  • different genes control different characterists e.g. eye colour
  • A-sexual reproduction does not involve joing of two gametes, all genetic info comes from parent= NO VARIATION
  • identical copies produces by a-sexual reproduction= CLONES
  • differences in characterists may be because of : 1)conditions e.g. sunny=tan 2) genes that have been inherited e.g. brown hair
  • cloning in plants- cuttings and growing them= cheap and effective
  • but in animals- tissue culturing= more expensive but produces large numbers of top quality plant
  • animals can also be cloned by transplanting cloned ebyros to develop in a host animal  (genetically modified embryos are sometimes transplanted

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