Atlas of Human Chromosome Heteromorphisms

pp 11-31

Methods of Studying Human Chromosomes and Nomenclature. The Normal Human Karyotype

  • Gopalrao V. N. Velagaleti
  • , Vijay S. Tonk

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Ever since the elucidation of the correct human chromosome number (2n = 46) by Tijo and Levan [1], clinical cytogenetics has become an important branch of medical genetics. It was natural that this epoch-making discovery was soon followed by discovery of various numerical chromosomal abnormalities such as trisomy 21 [2], trisomy 13 [3], trisomy 18 [4] and sex chromosome abnormalities that included monosomy X [5], XXY [6] and XXX [7]. Several of these important observations were followed by breakthroughs in the technological aspects of cell cultures, which had been a stumbling block in routinely studying human chromosomes. Two independent investigators, Nowell [8] and Moorehead et al. [9], described a simple method of cell culture to study human chromosomes, thus paving the way for the clinical cytogenetics revolution.