This woman is genetically positive q

In the early 19th century, in a remote village in Venezuela, a woman named Maria Concepcion got married and gave birth to a child. What she didn't know was that her genes would affect her children and grandchildren for over 200 years, causing them great distress and even a number of them being afflicted with the disease because she carried Huntington's chorea mutation gene.

Huntington's chorea is a genetic disease that causes rapid brain cell death. Early on, there are only minor emotional or intellectual problems, followed by an erratic pace, as if drunk, which continues to progress to motor difficulties, inability to speak, and eventually death.

This woman carrying the Huntington's chorea mutation gene married and even after, has now reproduced more than 10 generations, has more than 18,000 descendants, of which 15,409 are alive (data as of 2000), has become a large family, but this family, is also the world's largest family suffering from Huntington's chorea, the family has several people suffering from Huntington's chorea, many of them And died.

Huntington's chorea

Huntington's chorea is a dominant gene control disease, this gene is located on chromosome 4, and the cause of the disease is very simple, normal people on chromosome 4 there is a repeated DNA sequence: CA, CA, CA, CA, CA, generally speaking, the normal gene will carry 9-26 times of repetition, as long as the number of repetitions does not exceed 35 times will not develop.

If the number of repeats is 35-39, the onset of the disease is possible and may or may not develop Huntington's chorea.

A number of repetitions above 40 will definitely develop, but the onset is later, usually above 30 years of age (the number of repetitions is related to the age of onset).

Several repetitions around 60-125 will result in onset at age 20 or younger.

Although the disease is inherited from both parents, it was found in 30 cases of maternal transmission and 25 cases of paternal transmission that 68% of paternal transmission had an increased probability of 2-66 repeats; 40% of maternal transmission had 1-4 repeats. So amplifications of more than 4 repeats are always associated with the father, where the higher the number of repeats carried the more likely the disease is to develop and the earlier the age of onset.

In other parts of the world, this disease is very rare and the probability of occurrence is not high. However, in this small fishing village in Venezuela, the disease is very common.

By definition, Huntington's chorea is a dominant gene, which means that as long as one of the alleles is abnormal, it will develop, and the onset will again show morbid states, such as drunkenness, unclear speech, and in severe cases, death. This disease seriously affects people's lives, then why this gene is not cleaned out by natural selection, but in this family to retain, and spread out?

Let's take a brief look at their lives.

Why didn't natural selection clean up the disease-causing gene?

The family mostly lives in a small fishing village on the west coast of Lake Maracaibo in Venezuela, where people live in poverty, and fish for a living, mostly without modern education, and with little awareness of the diseases, they suffer from.

Local marriages are also very early, and in the past, girls in traditional fishing families often became pregnant around the age of 12-13 and gave birth to a large number of children, even 12 children.

Even though some were already sick, they still wanted to have children because they wanted to have children to take care of them when they were sick.

What's more, the family has a very high rate of Huntington's chorea, and there is a great fear of the disease in the outside world, which leads to the fact that they usually have no other choice when choosing a spouse but to marry a family also affected by Huntington's chorea, which in turn leads to inbreeding and increases the incidence of Huntington's chorea in their offspring.

What's more, the onset of Huntington's chorea can be early or late, with some people developing or even dying before they reach adulthood, when they have not had time to marry and have children and their genes are not passed on.

However, a large number of people develop the disease after they marry and have children. For example, a man named Parr developed the disease around the age of 50, and before he developed the disease he was very healthy, just like a normal person, and in the era of lack of genetic testing, people could not confirm whether he had the disease by his physical performance, so he married and had children just like a normal person, but he was not expected to develop the disease at the age of 50, which means that his The offspring also have a 50% probability of developing the disease.

Silo, a 40-year-old man, was once a robust fisherman, but then developed the disease and his body twisted uncontrollably. And he has given birth to 14 children, 10 of whom have been diagnosed with Huntington's chorea.

(Nancy, a specialist in the study of Huntington's chorea, is also a Huntington's chorea sufferer and has lost several people in her family to the disease)

There was also a woman who said her husband died at age 38 because of Huntington's chorea, yet she had four children before her husband developed the disease, two of whom had developed it early and the other two, who appeared healthy, were not sure whether they were healthy or not at the onset of the disease.

The scary thing about this disease is that even normal people in the area don't know that they are the safe ones, and as soon as someone in the family gets sick, they worry that they are also sick and just haven't developed the disease yet.

So while not all of her 18,000 children and grandchildren have the disease, everyone is shrouded in the shadow of Huntington's chorea, and as soon as one person in the family develops the disease, they become anxious that this doom will happen to them as well.

So you see, Huntington's chorea is very tricky; instead of causing death in infancy, as some diseases do, a lot of people will develop it after they marry and have children, by which time their genes have spread. And since natural selection selects by survival and reproduction, even if Huntington's chorea threatens people's lives, there is some chance that the gene will be preserved, as long as it does not interfere with human reproduction.

Unless, of course, the woman in Venezuela in the early 1800s who carried the mutated disease-causing gene did not marry and have children, or if her children did not happen to inherit her disease.

Although there is no particular solution for Huntington's chorea today, genetic testing is available to check for this disease in fetuses.

Huntington's chorea is only one of the known diseases, and there are many others for which we do not even know why we have the disease, not to mention finding a solution.