One in 500 men may carry an extra sex chromosome – an X or Y – but it is likely that very few of them know, a new study suggests.
The study, published in the June 9 issue of the journal In Genetic Medicine (Opens in new tab), Including data from more than 207,000 men who provided information to the UK Biobank, a repository of the genetic and health data of half a million participants in the UK. Males usually have an X and Y-shaped sex chromosome in each of their cells, but among the study participants, there were 213 men with an additional X chromosome and 143 with an additional Y.
Very few of these men reported having been diagnosed with a chromosomal abnormality or had reported such an abnormality in their medical records: of the XXY men, only 23% had a specific diagnosis, and 0.7% of the XYY men had a diagnosis. (The potential symptoms of having an extra Y chromosome can be very subtle, which may explain some of the difference in diagnostic rates, Genetic and Rare Diseases Information Center (Opens in new tab).)
“We were amazed at how common this is,” said Dr. Ken Ong, a pediatric endocrinologist and research author at the University of Cambridge’s Medical Research Council (MRC) Epidemiology Unit. he told The Guardian (Opens in new tab). “It was thought to be quite rare.”
According to previous estimates, between 100,000 and 200 men out of 100,000 are XXY, National Institute of Human Genome Research (Opens in new tab)and believed to be XYY from 100,000 to 18, the authors noted in their report.
Related: Does the Y chromosome disappear?
Overall, about 0.17% of the study participants had an additional sex chromosome, or about 580. However, the rate observed in the study may be slightly lower than in the general population, according to the authors of the study. This is because UK Biobank volunteers tend to be healthier than the general population and have a lower average incidence of genetic conditions. Based on this, the authors estimate that one in 500 men in the general population, or 0.2%, has an additional sex chromosome.
Having extra sex chromosomes may increase the risk of certain health conditions, and this increased risk seemed to be reflected in the health data of Biobank volunteers, the researchers reported.
For example, Klinefelter’s Syndrome (KS) – or having an extra X chromosome as a male – has been linked to reproductive problems, including infertility and delayed puberty, according to the National Institute of Human Genome Research. In the study, the childless rate of XXY men was four times higher than that of XY men, and three times more likely to start puberty late, according to one. statement (Opens in new tab).
The authors reported that 47, the condition known as having XYY syndrome or an additional Y chromosome as a male was not associated with an increase in the rate of reproductive problems. However, in the past, the syndrome has been linked to other symptoms, including learning disabilities, delays in speaking and motor skills, and unusual low muscle tone, according to the Genetic and Rare Diseases Information Center. These symptoms were not particularly evaluated in the biobank study.
Related: Are you more genetically similar to your mother or father?
However, the study revealed a possible link between separate sex chromosomes and other conditions. Compared to XY men, both XXY and XYY men showed higher rates of type 2 diabetes; plaque buildup in artery walls (atherosclerosis); blood clots in the veins (true thrombosis) and pulmonary arteries (pulmonary embolism); and chronic lung disease, which impedes airflow lungs.
“It is not clear why KS and 47, XYY need to show significant similarities in order to pose significantly higher risks for many common diseases,” the authors wrote in their report. They said the mechanisms that drive this high risk should be explored in future research.
The study is limited in that it includes only men of European ancestry between the ages of 40 and 70. However, “our study is important because it comes from genetics and tells us about the health impacts of having an extra sex chromosome. Associate Professor of Human Genetics at the University School of Medicine and co-author of the research. he said in the statement.
Originally published in Live Science.