Word: mendelianism
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...Chromosomes. For a while, as often happens after a scientific breakthrough, additional discoveries came easily. Several biologists, notably Walter S. Sutton in the U.S., connected Mendelian inheritance with the known behavior of chromosomes, which are threadlike bodies in the nuclei of cells. When a cell divides nonsexually, as in a growing plant or animal tissue, the chromosomes replicate (make copies of) themselves. Each daughter cell gets a full set, and unless something has gone wrong, it is exactly like the chromosome set of the parent cell (see diagram...
...large populations of fruit flies, a few are apt to be naturally defective, with stunted wings or misshapen limbs. In some cases these defects are inherited in a Mendelian manner, like the color of Mendel's flowers. Some traits are dominant, others recessive. They are caused by mutations (damaged genes) in the flies' chromosomes (they have only four pairs), and Morgan's method was to study every possible way that mutations could be passed from generation to generation...
Like harelip and cleft palate (TIME, Sept. 17), mental retardation may show up oftener in certain families without being directly hereditary by any Mendelian pattern. Dr. Stott's theory: the tendency may be hereditary, and disease or distress during pregnancy may touch...
...molecular structure from the normal Hemoglobin A. More important, Pauling & Co. showed that a defective gene determined the production of this type of hemoglobin. If both parents had the defective gene, even without the overt disease, the chances that their offspring would have full-fledged anemia were (by Mendelian law) one in four...
Geneticists believe that dwarfism is a classic example of Mendelian inheritance, and that it is caused by a single recessive gene. A bull may appear normal, but if it carries the gene of dwarfism and is mated to a carrier cow, one-quarter of their progeny will on the average be dwarfs, one-half will be carriers, and one-quarter will be dwarf-free. If the carrier bull is mated to a dwarf-free cow, no dwarfs will appear in the first generation, but half of the calves will be carriers...