Why is it dangerous to have an extra sex chromosome?
Geneticists have found that about one in five hundred men has an extra sex chromosome, which increases the risk of developing certain diseases. At the same time, the vast majority of carriers of an extra chromosome know nothing about this.
Sex chromosomes determine our biological sex. As a rule, their set consists of only two pieces. For women it is customary to designate XX, for men — XY. However, some males may have an extra X or Y chromosome, in which case this set will look like XXY or XYY.
Scientists from Cambridge University, together with Finnish and German colleagues, analyzed data stored in UK Biobank — a medical and genetic database containing anonymous information about the lifestyle and health of half a million Britons. We used information about more than 200 thousand men aged 40 to 70 years.
As a result, 356 of their extra sex chromosome was found: an extra X chromosome, y 143 — Y chromosome. And because this database contains data about people who are healthier than the general population, the researchers assumed that the percentage of such men is somewhat higher at the population scale. And exactly — 0.2%, then is about one in five hundredth.
But most carriers of the extra chromosome do not suspect this. According to the UK Biobank, only a minority of these people had an abnormality in their medical records. The fact is that it is impossible to identify it without a genetic test. Sometimes this happens when a man is examined for delayed puberty or infertility, in other cases, information about the extra chromosome remains unknown to him.
And after all, this information makes it possible to predict the risk of developing certain diseases, which will help to recognize them in a timely and prescribe treatment. This is the most important part of the study published in the journal Genetics in Medicine. As scientists have found, men with an extra sex chromosome are 3 times more likely to suffer from type 2 diabetes, 6 times more often — from venous thrombosis. They are 3-4 times more likely to have pulmonary embolism and chronic obstructive pulmonary disease.
Particularly unlucky men with an extra X chromosome, (type XXY) . In addition to the listed diseases, they 3 times the risk of delayed puberty and 4 times the risk of infertility. These people have significantly reduced testosterone concentration — natural male hormone. As for the carriers of the extra Y-chromosome, they do not have reproductive problems. The only thing that distinguishes them from other men — it's a taller height.
“We'll need more research to evaluate if there's an added benefit of wider screening for chromosomal abnormalities in the general population. But potentially, this provides an opportunity for early intervention that will prevent the development of relevant diseases, — the authors of the work explain in the article.
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