Shulou(Shulou.com)11/24 Report--

Jeanne Nollman, an American girl, is no different from her own sister. They are both beautiful and want the attention of their male classmates. However, by the age of 13, she found that she was not only different from her sister, but also different from other female classmates.

Jeanne Nollman (photo source: twitter.com/ jeannenollman) the biggest difference is that her 11-year-old sister and many other girls in the class have begun to develop, while they have been slow to move. She is often laughed at by her classmates because of her tall, thin, flat and muscular figure.

Jeanne Nollman (left 1) and her family (photo: Mystery Diagnosis) as a teenager still did not show up for her period at the age of 16. Then she began to worry. The doctor gave her various tests and found that she was not only underdeveloped, but also had an "ovary" to be removed.

The doctor said that although her "ovaries" did not develop, they had a high risk of cancer, so they needed to be removed. Nollman does not understand why her ovaries do not develop, nor does she understand why undeveloped ovaries need to be removed. It took her many years to learn that the doctor had concealed from her the fact that she was actually XY.

Many people think that if you have XY chromosomes, you must be a boy, whereas if you are XX, you must be a girl. But biology is not one size fits all. Some XY are actually girls.

(photo source: wikimedia) this is the case with Swell's syndrome (Swyer Syndrome).

The 23rd pair of chromosomes in patients with Sewell's syndrome is XY, which means they should be male in terms of chromosomes. However, they have female bodies, and most of them think they are women.

How can XY change into a girl?

It starts with the weak and helpless Y chromosome.

Comparison of X and Y chromosomes (Photo: wikimedia) compared with X chromosomes and other autosomes, Y chromosomes are really too short to carry much genetic information to pass on.

Although the human Y chromosome is short, it is not completely useless. The genes that determine the birth of boys and girls are on the Y chromosome. In humans and almost all mammals, there is a region on the Y chromosome that determines the sex of the fetus, which is the sex-determining domain Y protein (SRY) gene.

The SRY gene is located on the Y chromosome (photo: wikimedia) but SRY does not come out to work as soon as it is fertilized, it does not come online until the embryo has grown nipples and mammary glands.

In fact, all embryos are female at first, and male and female differentiation begins in the second month of embryonic development, which is why boys also have breasts-nipples and mammary glands grow out before sex differentiation.

Six weeks later, male and female embryos begin to differentiate, and one of the most important roles is the SRY on the Y chromosome. SRY can cause embryos to grow testes and other primary sexual characteristics.

However, if something goes wrong with SRY, the embryo will not have balls. Without eggs, there would be no testosterone, there would be no male gonads, and the embryo would continue to develop according to the default female version, continuing to grow the uterus and birth canal, which is why people with Swell syndrome appear to be girls.

American actress and director Arisleyda Dilone is an open sufferer of Swell's syndrome (photo: wikipedia), but the womb of a patient with Swell's syndrome has failed after all.

Because XY is not compatible with female body hardware after all, most girls in this version of XY do not have available ovaries, so they do not produce estrogen, go through puberty, and therefore do not have secondary sexual characteristics.

In other words, most people with Swell syndrome neither menstruate nor have children. Even when they reach puberty, the patient will continue to be a young girl. This is the root of the problem that bothers Nollman.

(photo Source: pexels) such incompatible chromosomes can also cause fatal damage to patients.

In fact, the gonads of patients with Swell's syndrome are often cord-shaped and prone to tumors, so their gonads are often removed after diagnosis and then need to take hormones for life.

So what causes the Y chromosomes of patients with Swell's syndrome to lose their original function?

A recent new study uncovers a mechanism behind it.

In short, some people with Swell syndrome do not develop into ordinary men because of the lack of an oxygen atom.

The team of Michael Weiss, a genetics researcher at Indiana University School of Medicine, found a mutation in a segment of the SRY gene on the Y chromosome of some patients with Swill's syndrome, causing tyrosine, which SRY should have expressed, to turn into phenylalanine, which is only one oxygen atom away from phenylalanine, which prevents XY from becoming a male.

(photo source: scitechdaily) specifically, although this tyrosine is not directly involved in the "masculinization" process, it acts as a DNA clip, prolonging the time of transcription (reading and expressing DNA), that is, the time of "masculinization".

In fact, all mammals have this "clip", and this mechanism also exists in some animals that are closely related to mammals, so it can be seen that this "clip" is very ancient and important.

However, if tyrosine is replaced with other amino acids, the clip will fail, and there may be problems with the transcription (reading) of DNA, which will prevent XY from becoming a boy.

DNA is similar to the human assembly manual, it takes a complex process of reading (transcribing) to create "you", in which some components (proteins) are first made and then further involved in your manufacturing and assembly process, as is the case with tyrosine encoded on SRY. (photo source: quizziz)

We have just mentioned "some" patients with Swell syndrome because some patients with Swift syndrome inherit their Y chromosomes from their parents, while others come from mutations. The Y chromosome with a difference of one oxygen atom in the above study is obtained by heredity.

Genetic tests after the death of Polish-born American Olympian Stanis Stanis awa Walasiewicz confirmed that she was a patient with Swell syndrome (photo source: wikipedia). You may be surprised that the Y chromosome still comes from your mother.

Yes, there are such miracles in medicine.

Although most people with Swell syndrome are infertile because they do not have mature ovaries, medical records show that one patient with Swell syndrome conceived naturally and gave birth to a baby. She had not discovered that her sex chromosome was XY until her daughter was diagnosed with Swift's syndrome.

In 2008, researchers first reported cases of children born in patients with this syndrome in the Journal of Clinical Endocrinology and Metabolism (Journal of Clinical Endocrinology & Metabolism).

(photo Source: pexels) researchers found that the Croatian mother actually had ovaries, which could explain why she was able to give birth.

However, her ovaries are very strange, with 93 per cent of the cellular sex chromosomes being XY,6%, with only one X chromosome and less than 1 per cent being XX. In other words, she is not only a patient with Swell syndrome, but also a Chimera (chimera) with different chromosomes in different cells.

After investigation, the researchers found that there were many girls in the mother's family who had no significant secondary sexual characteristics and were infertile, meaning her Swell syndrome was hereditary.

What is even more bizarre is that the mother not only looks like a normal woman, but also goes through a normal menopause. But her daughter is a typical patient with Swell syndrome. Similar to the Nollman mentioned in the post, the 17-year-old girl is very tall and thin, weighing only 68kg at 181cm.

This rare case shows that Swell's syndrome also has matrilineal inheritance.

In fact, similar families of Swell syndrome have been found in our country. E Zheng, a researcher at the Beijing Institute of Oncology, and colleagues have reported that five of the eight sisters in a family were diagnosed with Swell syndrome, while half of the eight sisters had similar tumors.

Because mammals have SRY, not only humans, but also some animals, such as XY's mares and mice, also have XY to give birth to children.

(photo Source: wikimedia) of course, looking at human society as a whole, the possibility that XY is a girl is not high. According to a review by University of Pittsburgh researcher Selma Feldman Witchel, only about one in 100000 women suffers from Swift's syndrome.

But that doesn't mean humans can let their guard down. in fact, the Y chromosomes of humans and other mammals have been slowly collapsing.

Weiss said that from an evolutionary point of view, the sex chromosomes of all animals degenerate over time, and the Swell syndrome caused by the absence of oxygen atoms is a dangerous example.

In short, it is very difficult to become a real man, even evolution is a stumbling block.

Don't ask why boys also have breasts, that may be the back way left by genes.

Reference:

Https://docs.qq.com/doc/DVHhKcVhDa1hxaFVC

This article is from the official Wechat account: bring Science Home (ID:steamforkids), author: everything, written by Seven Jun

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.