Tall and handsome long-legged little brother, may be XXY, this kind of disease is not uncommon

This chromosome abnormality, which often causes infertility, is called Klinefelter syndrome, where boys have one or more extra X chromosomes in addition to XY chromosomes.

The history of discovery and research of this disease is less than one hundred years. In 1942, American secretologist Harry Klinfeld (Harry Klinefelter) discovered Kirschner syndrome and found its cause more than a decade later-the extra X chromosome.

What will an extra X chromosome do to a boy?

To put it simply, Kirschner syndrome does no harm in addition to making patients look younger, more prone to infertility and learning disabilities such as dyslexia.

The symptoms of Kirschner syndrome mainly occur during puberty. With an extra X chromosome, patients have lower levels of testosterone (a testosterone) than the average boy, making it difficult for them to grow muscles and body hair, have long legs and have childish facial features.

Because of the extra X chromosome, boys with Kirschner syndrome have breasts that even develop like girls, so they are a little more likely to develop breast cancer than the average man (but still lower than women).

Extra X chromosomes can also cause patients with Kirschner syndrome to develop some special physical structures, such as their little fingers are usually bent in, and are also prone to bovine dental disease (pulp cavity abnormalities).

Extra X chromosomes can also affect the brain and mindset. From a cognitive point of view, patients with Kirschner syndrome have weaker language skills, are more likely to have learning disabilities, and are more likely to suffer from mental disorders such as anxiety and depression. However, their comprehensive IQ is no different from that of ordinary people.

So, will Kirschner syndrome be passed on to the next generation?

Kirschner syndrome is not hereditary, which means it is not passed on to the next generation because it is caused by random errors in meiosis.

What we learned from high school biology class is that eggs and sperm carry only half as much genetic material as they do because they undergo meiosis.

However, there are also errors during meiosis, such as the mother's two X chromosomes did not split properly, resulting in filling into one of her eggs. Of course, the father's XY chromosome may also have such an error.

As a result, part of the Kirschner syndrome comes from the mother's egg abnormalities and partly from the father's sperm abnormalities. Current studies have found that older women are a risk factor for Kirschner syndrome, and most of the extra X chromosomes in patients with Kirschner syndrome come from their mothers.

Of course, it is the reproductive ability and supporting hardware that are most affected by the excess X chromosome.

Boys with Kirschner syndrome have shorter genitals than ordinary boys, but Kirschner syndrome does not affect their lifespan.

With an odd number of chromosomes, Kirschner syndrome faces reproductive barriers: how do germ cells meiosis? An odd number divided by two is not an integer.

Meiosis

This is why the biggest disadvantage of Kirschner syndrome is that it may cause infertility. However, not all patients with Kirschner syndrome are infertile, and about half of patients with Kirschner syndrome can produce sperm.

In fact, Kirschner syndrome is the most common chromosome abnormality. According to the Mass version of Mercadon's diagnosis and treatment Manual, one in 500 newborn boys suffers from Kirschner syndrome. In other words, a university that recruits 5000 freshmen a year (assuming half men and women) usually welcomes five patients with Kirschner syndrome each year.

However, many people do not know that they have Kirschner syndrome. According to the 2013 publication in? Journal of Clinical Endocrinology and Metabolism? 1/4 of patients with Kirschner syndrome are unaware of their chromosomal abnormalities for the rest of their lives, according to a review of the study.

Kirschner syndrome has such a high incidence that it is impossible not to be exposed to it in daily life. In fact, many celebrities are people with Kirschner syndrome, and you can see both "male" and "female" in it.

Many scholars have long suspected that George Washington, the founding father of the United States, may be suffering from Kirschner syndrome because his wife gave birth to him before she married him, but did not give birth to any children in her 40-year marriage.

As evidence, in addition to infertility, Washington also has other features consistent with Kirschner syndrome, such as slender stature (he is 1.9 meters tall) and bovine dental disease (abnormal dental pulp cavity) that is common in people with Kirschner syndrome. However, Washington also has characteristics that do not conform to Kirschner syndrome, such as his strong speech ability, good speech, muscular and athletic love.

Robert Lahita, dean of the medical school at Beth Israel Medical Center in Newark, firmly believes that Washington is suffering from Kirschner syndrome. Of course, other possibilities have been raised. In 2004, John K. Amory, a researcher at the University of Washington School of Medicine, pointed out that tuberculosis in Washington may also be a major cause of his infertility.

In modern times, British supermodel Caroline Cossey, who was born in 1954, is a patient with Kirschner syndrome. She starred in the James Bond film "Top Secret" (For Your Eyes Only) in 1981. She was born a boy, but was later diagnosed with Kirschner syndrome at the age of 17 and subsequently received hormone therapy.

South African supermodel Lauren Foster was thought to be male at birth but became female after being diagnosed with Kirschner syndrome. She tried to take part in the Miss South Africa beauty pageant as a woman, but was rejected by the organizing committee.

South African athlete Caster Semenya, an Olympic gold medalist who was once famous for gender definition, is also suffering from Kirschner syndrome. She has a male face and a female chest, and competes as a woman. Of course, her special identity has also caused great controversy.

Thanks to modern genetic technology, researchers have dug up the ancients and found that many "men" or "women" in history are actually patients with Kirschner syndrome.

For example, the famous ancient Egyptian pharaoh Tutankhamun is an example. A study published in the Lancet in 1973 found that Tutankhamun had Kirschner syndrome and that "he" had too large breasts for men.

A study published in 2021 in the European Journal of Archaeology (European Journal of Archaeology) analyzed the DNA of a millennium-old female warrior in Finland and found that TA, who was buried in a high standard, was also a patient with Kirschner syndrome.

In fact, you can also see animals with XXY chromosomal skin in your life. Because XXY individuals may appear not only in humans, but also in mice, cats, horses and sheep.

Mice, for example, may develop XXY, so a large number of studies on Kirschner syndrome are done in rodents.

If you meet a male cat with three flowers or hawksbill turtle, it must also be XXY.

Most of the three-flowered cats are female, very few are male cats, these male cats are XXY, and most of them are sterile.

In mammals, in female somatic cells, only one of the two X chromosomes is expressed (that is, used), which is called X chromosome deactivation, and the other is sealed as Pap bodies (it's really comfortable not to work).

The cat's flower color is expressed on the X chromosome, with one gene specifying orange or black and another gene specifying white spots. Since a normal male cat has only one X, it will not be sealed, so the normal male cat will either become a big orange (all emperor yellow or yellow and white), black and white or all black.

On the other hand, one of the two X chromosomes of the female cat has been turned off. if the gene version on one X of the female cat is orange and the other is the allele that expresses black, then there