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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.
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.
Decades of research have demonstrated that both genetic and environmental factors play a role in a variety of behaviors in humans and animals (e.g. Grigorenko & Sternberg, 2003). The genetic basis of aggression, however, remains poorly understood. Aggression is a multi-dimensional concept, but it can be generally defined as behavior that ...
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.
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 ...
48,XXYY syndrome is a condition related to the X and Y chromosomes (the sex chromosomes). People normally have 46 chromosomes in each cell. Two of the 46 chromosomes, known as X and Y, are called sex chromosomes because they help determine whether a person will develop male or female sex characteristics. Females typically have two X chromosomes ...
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 ]
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 ...