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In the wake of the establishment of the normal number of human chromosomes, 47,XYY was the last of the common sex chromosome aneuploidies to be discovered, two years after the discoveries of 47,XXY, [27] 45,X [28] and 47,XXX [29] in 1959. Even the much less common 48,XXYY [30] had been discovered in 1960, a year before 47,XYY.
The presentation of XYYY syndrome is variable and at this time not entirely clear. As all known cases were diagnosed postnatally (after birth), and the similar XYY syndrome is known to have a milder phenotype in prenatally than postnatally diagnosed cases, it is suspected that many cases of XYYY syndrome may be mild or asymptomatic.
Nine of the patients, ranging from 5 ft 7 in (1.70 m) to 6 ft 2 in (1.88 m) height, were found to have an extra Y chromosome, the XYY syndrome. [20] [21] [22] Jacobs hypothesized that men with XYY syndrome are more prone to aggressive and violent behavior than males with the normal XY karyotype, but the idea was later shown to be incorrect.
Results from several decades of long-term follow-up of scores of unselected XYY males identified in eight international newborn chromosome screening studies in the 1960s and 1970s have replaced pioneering but biased studies from the 1960s (that used only institutionalized XYY men), as the basis for current understanding of the XYY genotype and ...
XYYYY syndrome, also known as 49,XYYYY, is an exceptionally rare chromosomal disorder in which a male human has three additional copies of the Y chromosome. Only seven non- mosaic cases of the disorder have ever been recorded in the medical literature, as well as five mosaic cases, of which two had more 48,XYYY than 49,XYYYY cells. [ 1 ]
In 1967 the MRC in Edinburgh launched a longitudinal study of infants, in order to determine the prevalence of sex chromosome disorders and to track outcomes of people born with them; the study was launched due to sensational publications claiming that XYY males were doomed to become aggressive and criminal adults. [4]
By the time of Linden, Bender, and Robinson's seminal review of sex chromosome tetrasomy and pentasomy in 1995, five cases of XXXYY syndrome had been reported. [3] As of 2023, three cases of XXXYY syndrome have been diagnosed in the 21st century. [2] Early research on sex chromosome aneuploidies suffered from ascertainment bias. Patients were ...
Despite her work being on XXY syndrome, the XYY syndrome is instead sometimes called Jacobs syndrome: [6] After it had been incidentally discovered by Avery Sandberg in 1961, [7] the syndrome was also found in a chromosome survey of 315 men at a hospital for developmentally disabled, made by Jacobs and hence considered the first little research ...