ABSTRACT
The field of medical genetics is rapidly expanding. Genetics is becoming increasingly important in the general practice of medicine. Ideograms are schematic representations of banding patterns used by cytogeneticists to standardize numbering of specific bands. The older method, quinacrine banding, or Q-banding, produces the same dark and light patterns, but requires the use of a fluorescence microscope and is used routinely. However, mosaicism for many different autosomal trisomies, that is, the presence of both normal and trisomic cells in one individual, has been described in viable infants. In polygenic inheritance, multiple genetic influences in combination act together to produce a disorder. In multifactorial disorders, there is no evidence to suggest simple Mendelian inheritance. Genetic counseling involves the explanation of the manifestations of the disorder, the natural history and treatment, the inheritance pattern, the risks of recurrence, and the methods of prenatal and postnatal diagnosis.
