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February 4, 1961

Trisomy of a Large Chromosome

Author Affiliations

Division of Medical Genetics Johns Hopkins University School of Medicine Baltimore.

JAMA. 1961;175(5):414-415. doi:10.1001/jama.1961.03040050070027

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To the Editor:—  In their report in The Journal, Sept. 17, page 221, on a mentally defective patient with mongoloid characteristics, Dr. Sandberg and his colleagues interpret their chromosome analysis as indicating trisomy of the 6th chromosome—a hitherto undescribed anomaly. In view of the observation of a double complement of sex chromatin in 70% of oral mucosal nuclei, it would seem that a more realistic conclusion is that the patient is another example of the triple-X syndrome (Jacobs and others: Lancet2:423 [Sept. 20] 1959; Jacobs and others: ibid.1:1213 [June 4] 1960; Stewart and Sanderson: ibid.2:21 [July 2] 1960; Ferguson-Smith, Handmaker, and Hill, to be published).The authors dismiss this possibility on the basis that the arm-length ratios of the trisomic chromosomes are not characteristic of the X-chromosomes, and also that the X-chromosomes may be separately identified by virtue of heteropyknosis. However, no measurements are

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