Everything about Xyy Syndrome totally explained
XYY syndrome is an
aneuploidy of the
sex chromosomes in which a
human male receives an extra
Y chromosome, producing a
47,XYY karyotype.
Some medical geneticists question whether the term "
syndrome" is appropriate for this condition because its
phenotype is normal and the vast majority (an estimated 97% in the UK) of 47,XYY males don't know their
karyotype.
Physical traits
Most often, the extra Y chromosome causes no unusual physical features or medical problems. 47,XYY boys have an increased growth velocity during earliest childhood, with an average final height approximately 7 cm above expected final height. Severe
acne was noted in a very few early case reports, but dermatologists specializing in acne now doubt the existence of a relationship with 47,XYY.
Testosterone levels (prenatally and postnatally) are normal in 47,XYY males. Most 47,XYY males have normal sexual development and usually have normal fertility. Since XYY isn't characterized by distinct physical features, the condition is usually detected only during genetic analysis for another reason.
Behavioral characteristics
47,XYY boys have an increased risk of
learning difficulties (in up to 50%) and delayed speech and language skills. In contrast, a national survey of US children conducted in 2004 for the
CDC found that 10% of 47,XYY boys had a learning disability.
As with
47,XXY boys and
47,XXX girls,
IQ scores of 47,XYY boys average 10–15 points below their siblings.
Developmental delays and behavioral problems are also possible, but these characteristics vary widely among affected boys and men, are not unique to 47,XYY and are managed no differently than in 46,XY males.
In some cases, the addition of an extra Y chromosome results from nondisjunction during cell division during a post-zygotic
mitosis in early embryonic development. This can produce 46,XY/47,XYY
mosaics.
47,XYY was the last of the common sex chromosome aneuploidies to be discovered, two years after the discoveries of
47,XXY,
45,X, and
47,XXX in 1959. Even the much less common
48,XXYY had been discovered in 1960, a year before 47,XYY. Screening for these
X chromosome aneuploidies was possible by noting the presence or absence of "female" sex chromatin bodies (
Barr bodies) in the
nuclei of
interphase cells in
buccal smears, a technique developed a decade
before the first reported sex chromosome aneuploidy.
An analogous technique to screen for
Y chromosome aneuploidies by noting supernumerary "male" sex chromatin bodies wasn't developed until 1970, a decade
after the first reported sex chromosome aneuploidy.
In December 1969, Lore Zech at the
Karolinska Institute in
Stockholm first reported intense
fluorescence of the
AT-rich distal half of the long arm of the Y chromosome in the nuclei of
metaphase cells treated with
quinacrine mustard.
Four months later, in April 1970, Peter L. Pearson and Martin Bobrow at the
MRC Population Genetics Unit in
Oxford and Canino G. Vosa at the
University of Oxford reported fluorescent "male" sex chromatin bodies in the nuclei of interphase cells in buccal smears treated with quinacrine dihdyrochloride.
Fictional depictions
A popular misconception in the 1960s and 1970s that XYY males were more prone to criminal behavior led to several novels and TV series which exploited the idea with little regard to the science.
Robin Chapman's 1971 episode of the BBC television science fiction series
Doomwatch (titled 'By The Pricking Of My Thumbs ...') portrayed the tragic results of this misconception being taken as fact by authority figures.
Less sympathetically,
Kenneth Royce's series of novels about
The XYY Man partially played up to the stereotype, with an anti-hero figure William 'Spider' Scott, whose extra Y chromosome is seen in part to be responsible for his career as a highly skilled (though non-violent) cat-burglar. Royce's books were turned into a TV series in the UK which ran 3 episodes in the summer of 1976 and 10 episodes in the summer of 1977.
In the film
Alien 3 (1992) the protagonist lands on a prison planet populated by XYY criminals, with the implication that they're more prone to commit assault, rape or molestation.
The short story "The Procrustean Petard," a Star Trek-based short story by Sondra Marshak and Myrna Culbreath, depicted a story where the crew of the Enterprise had their genders reversed, all but Spock who'd instead been given an extra Y chromosome. McCoy was concerned whether Spock's emotional control could handle the "hyper masculinity" the extra Y would cause, worried that he might become prone to emotional outbursts, even violence.
In the episode "Born Bad" of the show
Law & Order the defense strategy for Chris Paulit, a young boy accused of beating to death another boy, is his extra Y chromosome. Experts are called to testify that the XYY syndrome is more common among the prison population.
Further Information
Get more info on 'Xyy Syndrome'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://xyy_syndrome.totallyexplained.com">XYY syndrome Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
