ABSTRACT
The information from gene maps consists of two elements: information about the physical and the genetic map position. The physical map is established by assigning genes to particular chromosomes or regions of a chromosome. Genetic maps are constructed by studying the meiotic linkage relationships of gene loci. Chromosomes are prepared from leukocytes or from cultured fibroblast cells from male animals according to standard procedures. Usually several trials using blood cells from different animals are necessary to obtain preparations showing a satisfactory mitotic index. The distribution of autoradiographic silver grains is observed over the previously photographed chromosome spreads. The position of silver grains that are in contact with a chromosome is marked on prints of the metaphase spreads. The gene locus is then assigned to the two bands below the peak column and the two flanking columns.
