The theoretical model builds on the concept of continental drift developed during the first few decades of the 20th century. The geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the late 1950s and early 1960s. The lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken up into tectonic plates.
These disorders are known as monogenetic disorders (disorders of a single gene). Some examples of monogenetic disorders include: 1  cystic fibrosis, 2  sickle cell anemia,3  Marfan syndrome, 4  Huntington's disease, and.5  hemochromatosis.ome examples of monogenetic disorders include: 1  cystic fibrosis, 2  sickle cell anemia, 3  Marfan syndrome, 4  Huntington's disease, and. 5  hemochromatosis.
1 Only a few human diseases are triggered by a single gene working by itself. 2  In most cases, a disease results from the actions of many genes. 3  An example of a single-gene disorder is Huntington's disease, which was discussed in the last chapter. 4  One error in one gene leads to the fatal health problems of HD. Only a few human diseases are triggered by a single gene working by itself. 2  In most cases, a disease results from the actions of many genes. 3  An example of a single-gene disorder is Huntington's disease, which was discussed in the last chapter. 4  One error in one gene leads to the fatal health problems of HD.