THE SOMATIC CHOMOSOMES OF MAN

Until 1956 the somatic chromosome number of man was generally considered to be 2n = 48. In that year, however, observations were published that strongly indicated the real somatic number to be 46.1,2 This chromosome number was later confirmed by several other investigators, whose results are reviewed in a recent paper by Ford, Jacobs, and Lajtha.A Since 1956, only Kodani4 has reported human chromosome numbers other than 46, viz., 47 and 48. Ford, Jacobs, and Lajtha,3 in reporting the results of their studies on human bone marrow, also summarized all human cases with 46 chromosomes and arrived at a total of 60, excluding those of Kodani. To these can now be added all 13 individuals whose cells were studied in tissue culture at the Department of Biophysics, University of Colorado, Denver, in the autumn of 1957, and one case in which spermatogonial mitosis and meiosis were also examined. Thus the total number of individuals found to possess 46 chromosomes now stands at 74. The present paper deals with the analysis of the human karyotype of normal tissue cells grown in vitro by the methods previously described. In Table 1 the