This is from the perspective of eugenics, which is beneficial to the health of future generations. Inbreeding is closely related to the occurrence and continuation of genetic diseases. Whose children look like who, it is said that the offspring are similar or similar to their parents, which is called heredity. Inheritance is caused by the same genes in the body. Because consanguineous couples carry more of the same genes, some genetic diseases will only happen to their offspring when their parents have the same "pathogenic genes" and meet each other. In general marriage, this kind of "meeting" is rare. The situation of consanguineous marriage is different, and the chances of meeting each other are obviously increased. Because they come from the same ancestor, they have more common genes. There are 1/2 genetic similarities between parents and biological children, between brothers and sisters, and between grandparents, uncles, aunts, nieces and nephews. Cousins, cousins and aunts have the same 1/8 gene. There is116 genetic similarity between cousins, and 1/32 genetic similarity between cousins. The more the same genes, the more chances that the pathogenic genes meet, and the higher the incidence of genetic diseases.
Why can't close relatives get married?
There is a certain blood relationship between close relatives. If they get married, their descendants will have a great chance of getting an invisible genetic disease in your family.
Why can't relatives get married?
Third cousins or cousins within three generations are close relatives.
The harm of consanguineous marriage
Some young people, such as cousins or cousins, are close relatives in love and may often have such a question in their hearts. Will marriage have a bad effect on their future children? In other words, will you have children with genetic diseases or congenital malformations? If possible, what are the chances? They often come to the doctor with these questions for guidance.
Will consanguineous marriage have a bad influence on future generations? This question has been debated. In ancient times when human civilization was uncivilized, consanguineous marriage was very chaotic, with not only collateral blood relatives, but also lineal blood relatives. The rulers of ancient Egypt believed that only royal marriage could keep the purity and nobility of royal blood, so most of the people who got married were brothers and sisters. However, people draw a conclusion from countless facts: the marriage fertility rate of closely related men and women is low, the mortality rate of offspring is high, and congenital malformation and hereditary diseases often occur. In modern times, a large number of data prove that the incidence of dementia children is 150 times higher than that of non-consanguineous marriage, and the neonatal mortality and disability rate are more than three times higher than that of non-consanguineous marriage. It has also been reported that the number of children married by close relatives who died before the age of 20 reached 13.9%, while the number of children married by non-close relatives was only 1.7%. A large number of facts have proved that consanguineous marriage is not good for future generations and should be banned.
Therefore, Article 6 of China's new Marriage Law clearly stipulates that lineal blood relatives and collateral blood relatives within three generations are prohibited from getting married. Close relatives refer to people who are related by blood, more precisely, people who are not too far away from their ancestors, usually dating back to three generations ago. Why does consanguineous marriage increase the incidence of genetic diseases in offspring? This should be explained from the perspective of genetics. The inheritance of organisms is accomplished through the transmission of information by genes, which are the material basis of inheritance, and are transmitted to offspring through germ cells (* * * and eggs), so that parents' traits can be expressed in offspring. Each of us has about 50,000 genes, half of which come from our father and the other half from our mother. That is to say, there are 1/2 genes that may be the same between each child and parents, so there are 1/2 genes that may be the same between brothers and sisters. But there are 1/4 possible similarities between grandchildren and uncles. Similarly, there is a possible similarity of 1/8 between cousins. The pathogenic genes of some genetic diseases are recessive. If one parent carries this gene and the other parent does not, the pathogenic gene can be covered up, so the offspring will not get sick. Only when both husband and wife carry this recessive gene will their offspring get sick. As mentioned above, when close relatives get married, the possibility of both parties carrying the same gene is obviously greater than that of the general population. Taking albinism as an example, the disease is manifested as albinism of the whole body panel and hair. The frequency of carrying this pathogenic gene in the population is 1/50. If the relatives are not married, the probability of the offspring getting sick is110000. If cousins are married by close relatives, the probability of offspring getting sick is11600, which is more than 6 times higher than that of close relatives. At present, autosomal recessive genetic disease 1232 has been found. Besides albinism, other common diseases include congenital deafness's disease, microcephaly, phenylketonuria and galactosemia. Inbreeding will not only increase the incidence of recessive genetic diseases, but also increase the incidence of polygenic genetic diseases, such as hydrocephalus, spina bifida, anencephaly, schizophrenia, congenital heart disease, epilepsy and so on.
As can be seen from the above information, the adverse consequences caused by consanguineous marriage are scientifically based. With the improvement of cultural living standards, people have a deeper understanding of the prohibition of consanguineous marriage, which has been accepted by most people. However, there are still a few areas where the custom of marriage still prevails. There are also some people who give the opposite example. For example, some people say that Darwin, a British scientist in the19th century, is a descendant of a close relative. No bad consequences were found in him, and he was smarter than the average person. But these people don't know that Darwin gave birth to 10 children after marriage, of which 3 children died early and 5 children were infertile for life. Indeed, not all offspring of close relatives have mental retardation and genetic diseases. On the contrary, the offspring of consanguineous marriages are not absolutely normal, but only probability. Some young people, cousins since childhood, have established love relationships, knowing the risks, but insisting on getting married by luck. We hope these people believe in science, think about the happiness of their families and the health of future generations, and also think about improving the quality of our nation. Don't take this risk, or they will make a big mistake and regret it. ...
Why does the law now stipulate that close relatives cannot get married?
Up to now, there are more than 5,000 genetic diseases in human beings, more than half of which are single-gene genetic diseases. Because they are the same ancestor, the possibility of carrying the same pathological gene is much higher than that of ordinary unrelated people, that is, the probability of two pathogenic genes meeting increases, that is, the probability of genetic diseases increases. The results show that the incidence of recessive genetic diseases in random marriage population is only 0. 1% to 0.5%, while the incidence of recessive genetic diseases in consanguineous marriage is increased to 0. 1% to 0. 1%. At the same time, consanguineous marriage will also lead to the incidence of multi-network genetic diseases and the increase of neonatal and infant mortality, such as mental retardation, congenital heart disease, anencephaly, hydrocephalus, spina bifida and other polygenic genetic diseases, which are four times higher than the children of random couples. According to the World Health Organization, the mortality rate of female infants born in inbreeding is 8. 10%, while the children born out of wedlock are only 2.4.
Of course, there is another different view:
However, a new study completed by a famous American geneticist points out that the risk of giving birth to deformed children by inbreeding is far lower than people think. The host of this new study is Robin Bennett, a geneticist at the University of Washington. He said, "Today, consanguineous marriage still bears the responsibility of abnormal children. In fact, this statement lacks sufficient social and biological reasons. Many misinformation and false positives are obstacles and stumbling blocks for cousins who really love each other to have children. "
Bennett's research team includes many senior researchers from Stanford University and American Association of Genetic Consultants (NSGC). This new study lasted for more than two years, covering North America, Africa, Asia and the Middle East. They studied the health statistics of children born to the first generation of close relatives. The researchers concluded that the rate of inbreeding leading to cystic fibrosis (hereditary pancreatic disease) and recessive genetic diseases such as Tay-Sachs disease is 7%-8%. In the general population, the genetic ratio is 5%.
According to the new research, doctors and genetic counselors should pay attention to family history and provide routine fertility services, such as fetal examination during pregnancy and neonatal disease examination, instead of hindering the birth of close relatives. The new study was published in the April issue of the Journal of Genetic Counseling.
Although the results of the new study are surprising, some geneticists say they will continue to warn people to be cautious about inbreeding. Philip Reilly, the geneticist and author of the best-selling book "DNA in abraham lincoln" in the history of human genetics, said, "The heritability of 7%-8% of recessive diseases is nearly 50% higher than that of 5%. This is one of the main differences between consanguineous marriage and normal situation. For genetic counselors who target young men and women who are married by close relatives, this must be kept in mind. "
Scientists say that at least 5000 diseases are caused by recessive genetic factors. It doesn't matter if you only get one such genetic factor from one parent, but if you get one from both parents, the result is either a dead end or a lifelong chronic disease. Close relatives who get married have the same grandfather. If both parties get "bad genes", the child will suffer.
Congenital marriage is quite common in rural areas, one of the reasons is to ensure the safety of money and property in the family. This custom is still common in countries such as Saudi Arabia and Pakistan. Allen Byers, a genetic researcher, estimates that in all marriages in the world, consanguineous marriages account for about 20%. It is estimated that the ratio of consanguineous marriage in the United States is about11000. The main reasons are: Judaism and Christianity prohibit cousin marriage; Catholicism requires that this kind of consanguineous marriage must be approved by the church. There are 30 States in the United States that prohibit cousins from getting married.
Why can't close relatives get married? Why on earth? 50 points
The biggest problem of consanguineous marriage is that the children born are prone to defects, such as deformity or congenital diseases. This is a tragedy for any family.
Of course, we should also find out what inbreeding is. Some people think that as long as they are related by blood, they are close relatives regardless of distance. This is inevitably overkill.
Marriage law prohibits collateral blood relatives or lineal blood relatives within three generations from getting married. In the past, the common consanguineous marriage was between cousins.
Does the law prohibit consanguineous marriage?
Of course it is forbidden! There is no corresponding criminal law charge for consanguineous marriage, but the Hunger Marriage Law and related judicial interpretations stipulate that consanguineous marriage is invalid, and close relatives of both parties can apply to the court to declare the marriage invalid.
Why do China laws prohibit consanguineous marriage? What are the hazards of consanguineous marriage?
Why not advocate consanguineous marriage? Inbreeding is one of the most important contents of genetic counseling since its establishment. Article 6 of Chapter 1 of the Marriage Law passed by the Third Session of the Fifth National People's Congress in September 1980 clearly stipulates that it is forbidden to marry lineal blood relatives and collateral blood relatives within three generations. Marriage law is one of the national laws, and every citizen must abide by it. Some people envy the freedom of foreign countries and say, "It doesn't matter whether you are a close relative or not, you can go to church for a wedding if you want …" He can't be regarded as having a clear understanding of the meaning of freedom. Professor Allen Beattre, an internationally renowned anthropologist who specializes in consanguineous marriage, once praised: "China's marriage law is really a very good law, and legislation cares about the quality of the population. Unfortunately, there is no such law in Britain. " Others said: "Our family has never had a genetic disease for generations, and I firmly believe that we will never get a genetic disease at all." But after all, the questioner is still uncertain and wants to ask how to detect genetic diseases, so the next question is "We are willing to spend money on testing and ask you which hospital is the best for us to test?" In this regard, there is no need to talk about marriage law. Let's use scientific calculation to explain why inbreeding is not advocated. According to experts' estimation, every normal person may carry several or even a dozen harmful recessive alleles, and inbreeding will make these recessive alleles have more opportunities to meet and produce genetic abnormalities. Half of the human nuclear genome comes from father and half from mother. In the case of consanguineous marriage, the probability of combining two equally problematic genes is far greater than that of non-consanguineous marriage. What is the risk of inbreeding? Let's calculate from the following marriage pattern: if there is a gap between the first cousin and the second cousin that represents the intermarriage of the first cousin, then the consanguinity index is 1/32 = 0.03 125, and so on for other types. Suppose that the proportion of a genetic disease in the population is11000; the risk of non-inbreeding offspring is1/500x1/500x1/4 =1/kloc-0. The offspring risk of second cousin marriage is1/500×1/64×1/4 =1128000; The risk of offspring married by close relatives is 1/500× 1/60. The risk of the offspring of 32,000 sibling marriages is1/500×1/4×1/4 =1/8000. Compared with consanguineous marriage, the risk of second-degree relatives is 7.8 times higher. The risk of first-degree relatives increased by 3 1 times; The risk rate of sibling marriage is 125 times that of normal random marriage! If we follow the expert's advice, everyone may carry several or even 10 recessive harmful genes, and the risk of inbreeding offspring will be higher. For example, glycogen storage disease, an autosomal recessive genetic disease, has many possible types, and its gene consists of 17 exons. The married offspring of people with mutations in different exons will not be abnormal, and the pairing of two identical exons is usually caused by inbreeding. Some people say that intermarriage between different ethnic groups will increase the incidence of cancer, which is totally unfounded. Modern humans have no reproductive isolation and no species distinction. White people, black people and yellow people are all the same species, and their blood relationship is very close. For example, the molecular differences between blacks and whites may be smaller than the genetic differences between Beijingers and Shanghainese. This is a genetic definition, that is, the differences between individuals within a family may be greater than the differences between individuals within a family. Others take some ethnic minorities in our country as examples, saying that consanguineous marriage there makes everyone there beautiful, with double eyelids and big eyes, and so on, and to demonstrate the benefits of consanguineous marriage. This idea is natural, but this kind of propaganda is absurd and irresponsible. The characteristics of double eyelids are an important genetic feature. Because most ethnic minorities in the south have this genetic feature, it will be shown whether relatives are married or not, and it has nothing to do with the marriage of relatives. Whether a person is beautiful or not is more determined by internal factors. The size of eyes is a sign of crowd specificity. North China from China ......
Is there a law that close relatives cannot get married?
Biologically, it is known that consanguineous marriage will increase the probability of various diseases. The farther the consanguinity is combined, the greater the genetic advantage of offspring, just like why mixed-race children are generally beautiful! China's marriage law clearly stipulates that direct blood relatives and collateral blood relatives within three generations are forbidden to get married. Collateral consanguinity within three generations refers to the same lineage from grandparents (except direct consanguinity). Marriage between brothers and sisters (including half-brothers, half-brothers), cousins is prohibited according to law. Please remember: if you want to have a healthy child, don't marry a close relative! However, some people think that there is nothing wrong with consanguineous marriage, which is related to relatives.
Please look at a series of harsh facts:
In Maillasson, there are separate Awukas. Because we can only get married within our parents, all kinds of birth defects, dwarfism and polydactyly can be seen everywhere, leading to racial degradation and extinction.
In the tropical forests of central Africa, thousands of pygmies live. They are short and sickly, so they are called "lilliputian countries". Doctors found that they lack an insulin growth gene I in their bodies, and the fundamental reason for the lack of this gene is that the Pygmies still maintain the primitive and backward custom of consanguineous marriage.
There are many Jinuo villages in Yunnan, China. As a result of inbreeding, the population has never been rich. Once a famous girl was on the fortress, but now there is only an empty house and grave.
According to the survey of the World Health Organization, the incidence of mental retardation, congenital malformation and hereditary diseases caused by consanguineous marriage is 150 times higher than that of children married by non-consanguineous relatives, and the neonatal mortality rate is more than 3 times higher.
In Japan, 95% of parents of albinos are married by close relatives, and 85% of parents of dementia are married by close relatives. In Israel, 904 families of mental retardation patients were investigated, of which 75% were married by close relatives.
Why do children who are married by close relatives get genetic diseases easily? We know that every "healthy" person may have several recessive pathogenic genes. Only when parents have the same "pathogenic genes" and "meet" will the offspring show it, that is, they are obviously sick. In general marriage, this kind of "meeting" is extremely rare; However, this kind of "encounter" is obviously increased among couples who are married by close relatives, because they are closely related by blood, come from the same ancestor and have more common genes.
In nature, self-pollinating plants are often inferior to one generation and are often eliminated; Cross-pollination is superior. The same is true of human reproduction. Darwin, a famous British biologist, married his clever and beautiful cousin Emma and gave birth to 10 children. As a result, three people died, four suffered from mental illness and three were infertile for life.
Article 6 of China's Marriage Law clearly stipulates that it is forbidden to marry lineal blood relatives and collateral blood relatives within three generations. This is completely in line with the principles of eugenics. Love and marriage are free, but not just for two people. Although the descendants of close relatives are not necessarily genetic patients, they are much more likely to suffer from various recessive genetic diseases than the descendants of non-close relatives, so they should not take any chances, otherwise they will be happy for a while and regret for life.
Young men and women with close relatives, the best way to avoid marriage is to put out the fire of love rationally from the beginning, so as not to brew bitter fruit. According to modern human geneticists, if cousins can be completely banned from getting married, the incidence rate in congenital deafness can be reduced by 20%, the adolescent cataract *** 15%, xeroderma pigmentosum 50% and albinism 35%. Why not?
Why can't close relatives get married?
Couples who are closely related may get the same genes from their ancestors and pass them on to their children. If this gene is inherited by autosomal recessive inheritance, its children may get sick because they are homozygotes of mutation. So inbreeding will increase the risk of some autosomal recessive genetic diseases.
Why can't close relatives get married and have children? Why are children born bad?
Inheritance is caused by the same genes in the body. Because consanguineous couples carry more of the same genes, some genetic diseases will only happen to their offspring when their parents have the same "pathogenic genes" and meet each other. In general marriage, this kind of "meeting" is rare. The situation of consanguineous marriage is different, and the chances of meeting each other are obviously increased. Because they come from the same ancestor, they have more common genes. There are 1/2 genetic similarities between parents and biological children, between brothers and sisters, and between grandparents, uncles, aunts, nieces and nephews. Cousins, cousins and aunts have the same 1/8 gene. There is116 genetic similarity between cousins, and 1/32 genetic similarity between cousins. The more the same genes, the more chances that the pathogenic genes meet, and the higher the incidence of genetic diseases.