A Modification of the “Moorhead Technic” for Chromosomal Analysis

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THE purpose of this paper is to present a simple technic for the preparation of cells for chromosomal analysis. The origin of this technic dates from 1952 when Makino and Nishimura1 employed a technic involving water pretreatment fixation, and crushing of animal tissue. Sachs,2 in 1952, also described a hypotonic pretreatment squash technic that was used and was modified by subsequent workers.3

The type of tissue that was originally used for the determination of the chromosome number in man was neoplastic tissue, testicular tissue, or normal cells grown in vitro. Using these tissues and the aforementioned technics, the best estimate that workers could achieve of the correct diploid number of chromosomes in man was 48.4 However, in 1956, according to Ford and Hamerton,5 Tjio and Levan published observations on four therapeutically aborted Swedish embryos in which they could find only 46 chromosomes. Ford and Hamerton5 in the same year reported similar results in their study of the freshly removed testes of three men. Their preparations were made with the pretreatment with hypotonic solution, fixation with acetic acid and methanol, and the squash technic.

The arresting effect of colchicine upon growing cells has been known for many years.6 Thus it was natural that this drug should be used in the early technics for the examination of chromosomes in cells grown in vitro. Ford and Hamerton7 in 1956 published a method employing colchicine and hypotonic citrate before squashing the cells.

In 1958, Rothfels and Siminovitch8 suggested an air-drying technic to supplant the . . .



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