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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.
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.
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 ]
Though a 48-chromosome complement involving the autosomes would be unsurvivable, 49,XXXYY and other high-level sex chromosome aneuploidies, such as tetrasomy X, pentasomy X, XYYY syndrome, XYYYY syndrome, and XXXXY syndrome, are survivable with relatively mild phenotypes due to the paucity of genes vital to basic development on the sex chromosomes.
However, the experimental design had many flaws, including small sample sizes, biased sampling, and poor definition of the phenotype "aggression", resulted in the mischaracterization of XYY individuals as aggressive and violent criminals, which led the path for many biased studies on height-selected, institutionalised XYY individuals in the ...
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 ...
Offspring have two sex chromosomes: an offspring with two X chromosomes (XX) will develop female characteristics, and an offspring with an X and a Y chromosome (XY) will develop male characteristics, except in various exceptions such as individuals with Swyer syndrome, that have XY chromosomes and a female phenotype, and de la Chapelle Syndrome ...