My brother and I really love each other.

The offspring of two people who are related by blood will have problems, such as deformed children and mental retardation.

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 mating patterns:

If there is a gap between the first cousin and the second cousin that represents the intermarriage between the first cousin and the first cousin, the consanguinity index is 1/32, and so on for other types. Suppose the proportion of a genetic disease in the population is11000:

The risk of offspring of non-consanguineous marriage is11000000 (one in a million);

The risk of second cousin's married offspring is1128000.

The risk of the offspring of first cousin marriage is 1/32000.

The risk of offspring of sibling marriage is 1/8000.

Compared with non-consanguineous marriage, the risk of second-degree relatives increases by 8 times; 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 is composed of 17 exons. The married offspring of people with mutations in different exons will not be abnormal, but 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.

In addition, the incidence of polygenic genetic diseases is high, such as hypertension, schizophrenia, congenital heart disease, anencephaly, epilepsy and so on. The mortality rate of children born of consanguineous marriage is also significantly higher than that of children born of non-consanguineous marriage. To this end, many countries have passed laws prohibiting consanguineous marriage. Article 6 of China's Marriage Law stipulates: "lineal blood relatives and collateral blood relatives within three generations are forbidden to get married." Lineal consanguinity refers to the relationship between parents and children, grandparents and grandchildren, and grandparents and grandchildren. Collateral blood relatives within three generations include compatriots, uncles (aunts) and uncles (aunts). According to the survey, the rate of consanguineous marriage is about 0.7% in cities and 1.2% in rural areas. In some mountainous areas, rural areas and islands, due to underdeveloped transportation, the proportion of close relatives is high, so there are more genetic diseases.

example

As the most prominent and widely ruled royal family in European history, members of the Habsburg family once ruled Austria, Hungary, Belgium, the Netherlands, Germany and other European countries. However, in the18th century, due to the severance of male heirs, the family suddenly declined, and the reasons were puzzling. Spanish scientists have recently solved this mystery: incest and consanguineous marriage are the important reasons for the decline of this European royal family.

Scientific research report

Experts from Western Australia, Australia, have challenged the problem that human inbreeding will give birth to unhealthy babies. This highly controversial topic has been puzzling people. In the past, people always thought that inbreeding would give birth to deformed babies, who suffered from many diseases, such as heart disease, mental retardation, deafness and even blindness. In 200 1 year, a scientific report published by an authoritative magazine in Australia claimed that the probability of a cousin getting married and giving birth to a deformed child was three times that of a non-relative getting married and giving birth to a sick child. However, Allen Bito, a professor of comparative genomics at Murdoch University, has spent 30 years studying this topic and found that most of her cousins are healthy.

In Western Australia, Australia, about 500 couples get married through cousins. Professor Allen came to the conclusion through research: "In western culture, there is a general idea that cousin marriage leads to genetic tragedy, but a large number of facts have proved this idea wrong. Cousins can also give birth to healthy babies. "

Professor Bito conducted a survey in 1 1 countries, and found that the probability of giving birth to a deformed baby was 2%, while the probability of giving birth to a deformed baby by a close relative only increased to 4%. He also found that the infant mortality rate of close relatives is only 1.2%, which coincides with his research in 2002: the probability of a cousin getting married and giving birth to a deformed baby is less than 3%. This question triggered a heated medical debate at the medical seminar of the Royal Society of East London. Some researchers and politicians claim that in Britain, consanguineous marriage can lead to very serious consequences, and their children may be deformed or even die prematurely. The opponents represented by Professor Bito spoke: "As for the genetic tragedy of marriage, I think it is more related to excessive drinking and smoking." Many famous people, such as Einstein and Darwin, got married between their cousins. Cousin marriage is common in some countries, such as Pakistan, South Asia and Middle East countries.

In this debate, a doctor agreed with Professor Bito very much. He claims that there is only a 4% chance that the marriage between cousins will have a baby defect, which is nothing in genetics, so there is no need to worry about genetic problems at all.

Professor Bito said that it is wrong to say that cousin marriage is extremely rare. In fact, in many parts of the earth, cousins get married more frequently. The total population of these areas exceeds 654.38+0 billion, and about 20% to 50% of marriages there are related by blood. Professor Bito believes that as more and more immigrants enter Australia, more and more cousins will get married. In view of the large number of marriages between cousins, Bibitoggio called for further medical research on this issue in order to better explain this mystery.