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The recent development of tissue culture methods for human cells and improved techniques for the determination of the number and morphology of mammalian chromosomes have made possible the accumulation, within a period of a few years, of a large amount of data which have established the normal diploid number of chromosomes in human somatic cells as 46. This number comprises 22 pairs of autosomes and two sex chromosomes (XX in the female, XY in the male). In addition, the heredity
TRISOMY OF A LARGE CHROMOSOME. JAMA. 1960;174(3):299. doi:10.1001/jama.1960.03030030079019