Subscribe to the BioNews newsletter for free

Login
Advanced Search

Search for
BioNews

Like the Progress Educational Trust on Facebook




 

Females lacking second X-chromosome may have started life 'male'

14 September 2009

By Lorna Stewart

Appeared in BioNews 525

Turner Syndrome, a condition in which women have only one X chromosome instead of two, may be caused by a missing Y chromosome instead of a missing X as previously thought. Research published in Cell at the start of this month suggests that disruption in the Y chromosome can cause a range of male sex disorders including, surprisingly, Turner Syndrome which has always previously been considered a female sex disorder.

In females, the two X chromosomes can 'swap' sections of DNA during reproduction, a process known as recombination. Recombination helps to protect against the effects of deleterious mutations by ensuring a novel combination of gene material in the egg and the sperm, reducing the likelihood of a zygote carrying two X chromosomes with the same recessive mutation. However, the X and Y chromosomes are fundamentally different to each other and so cannot pair up and swap genetic material in this way. The Y chromosome has solved this problem by being 'palindromic' (having sections of DNA that are mirror images of other DNA sections) and instead recombining with itself during reproduction. The work published in the journal Cell this month has found further evidence for so-called 'self-recombination' in the Y chromosome, but also found that in some instances this process can cause more problems than it solves.

Professor David Page and his colleagues at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, US, analyzed the Y chromosomes of nearly 2,400 male patients with previously identified sexual abnormalities. They found that 51 of these Y chromosomes had two centromeres instead of one. So called 'isodicentric' Y chromosomes are inherently unstable and can fracture or even disintegrate entirely. Since the centromere is important for cell division, this Y-chromsome instability may have the potential to cause a range of disorders, according to Professor Page's work. He says: 'The same chromosome disorder [is] showing up in men who make few or no sperm but are otherwise healthy, and individuals who have various anomalies of sexual development at a broader anatomic level.'

Professor Page and colleagues have suggested that instead of a missing X chromosome, as previously thought, women with Turner Syndrome may in fact have a missing Y chromosome; A missing Y chromosome that may have disintegrated precisely because it was isodicentric and therefore unstable. 18 of the 51 patients Professor Page and colleagues found to have an isodicentric Y chromosome are anatomically female.

It is as yet unknown what proportion of Turner Syndrome cases can be explained by these findings. Professor Page suspects that these findings may be 'the tip of the iceberg.'

SOURCES & REFERENCES
Science Daily | 03 September 2009
 
Scientists find genetic cause of male infertility
The Times | 03 September 2009
 
EurekAalert | 03 September 2009
 
The Y-chromosome: when sex with yourself misfires
The Times | 03 September 2009
 
The Scientist | 03 September 2009
 

RELATED ARTICLES FROM THE BIONEWS ARCHIVE

17 October 2011 - by Daniel Malynn 
'Me, My Sex and I' is a documentary about people who are born neither entirely male nor female. I must state at the outset that this programme is about the sex of the individual, and should not be confused with gender, which is how people identify themselves (something that many other TV reviews have got wrong in describing this programme). As the show makes clear, sex is not an 'either or' for many people; the real buzz word here is 'ambiguous'....
09 May 2011 - by Dr Rosie Gilchrist 
New research suggests that pregnancy via egg donation, in women with Turner's syndrome, carries an increased risk for both mother and child...

HAVE YOUR SAY
Be the first to have your say.

You need to or  to add comments.

By posting a comment you agree to abide by the BioNews terms and conditions


- click here to enquire about using this story.

Published by the Progress Educational Trust
Advertise your products and services HERE - click for further details

Good Fundraising Code

Become a Friend of PET HERE and give the Progress Educational Trust a regular donation