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8.2 summarise the role of gene cascades determining limb formation in birds and mammals
summarise the role of gene cascades determining limb formation in birds and mammals
- During limb development in birds and mammals, an appropriate sequence of genes is turned on to form such things as bones, muscles, ligaments, tendons, nerves and blood vessels. As each gene is turned on, certain substances are produced that turn on the next gene in the sequence. This process is repeated and continues as the limb develops. This process of a sequence of genes being turned on which then causes other genes to be turned on is called a gene cascade.
- The CSIRO is currently studying the development of limbs in chickens. During embryonic development, cells that form limbs are specifically programmed to form either a leg or a wing. At this stage, scientists know about gene sequences after the cells are programmed to form a part of the body such as a leg, but they do not know very much about the gene cascade in the preprogrammed stage of development. They do not know the particular chemicals that will determine which cells will form a limb in the first place.