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Past thoughts on genetic factors influencing aggression, specifically in regard to sex chromosomes, tended to seek answers from chromosomal abnormalities. [4] Four decades ago, the XYY genotype was (erroneously) believed by many to be correlated with aggression.
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 two syndromes have a number of symptoms in common, such as tall stature (although the height increase in XYY appears greater than that in XYYY [1] [18]) and behavioural issues. One significant observed distinction is that while males with 47,XYY karyotypes usually have normal fertility, 48,XYYY appears associated with infertility or sterility.
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 ...
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]
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 ...
Sex chromosome anomalies belong to a group of genetic conditions that are caused or affected by the loss, damage or addition of one or both sex chromosomes (also called gonosomes). In humans this may refer to: 45, X, also known as Turner syndrome; 45,X/46,XY mosaicism, also known as X0/XY mosaicism and mixed gonadal dysgenesis; 46, XX/XY
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]