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In determining if a trait is related to genetic factors or environmental factors, twin studies and adoption studies are used. These studies examine correlations based on similarity of a trait and a person's genetic or environmental factors that could influence the trait. Aggression has been examined via both twin studies and adoption studies ...
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.
Findings from behavioural genetic research have broadly impacted modern understanding of the role of genetic and environmental influences on behaviour. These include evidence that nearly all researched behaviours are under a significant degree of genetic influence, and that influence tends to increase as individuals develop into adulthood.
The presence of the genetic profile is not determinative, although it increases the likelihood of delinquency in cases where other factors are present. Ferguson stated, 'a large percentage of our behaviour in terms of violence or aggression is influenced by our biology - our genes - and our brain anatomy.' [ 4 ] Schnupp stated, 'To call these ...
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 ...
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 ...