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XYY syndrome, also known as Jacobs syndrome, is an aneuploid genetic condition in which a male has an extra Y chromosome. [1] There are usually few symptoms. [2] These may include being taller than average and an increased risk of learning disabilities. [1] [2] The person is generally otherwise normal, including typical rates of fertility. [1]
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.
The field of psychology has been greatly influenced by the study of genetics. [1] 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 ...
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]
The SHOX gene in the PAR1 region is the gene most commonly associated with and well understood with regards to disorders in humans, [17] but all pseudoautosomal genes escape X-inactivation and are therefore candidates for having gene dosage effects in sex chromosome aneuploidy conditions (45,X, 47,XXX, 47,XXY, 47,XYY, etc.).
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.
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 aneuploidies [note 1] are generally associated with tall stature, particularly polysomies of the Y chromosome, but data on tetrasomy and pentasomy disorders [note 2] is less clear and some seem associated with short stature; [6] [7] adult XXXYY men in the medical literature have ranged in height from 170 centimetres (5 ft 7 in ...