Will the marriage of close relatives of parents affect our next generation?

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. If they marry, it is called consanguineous marriage. Close couples may get the same gene from their common ancestor and pass it on to their children. If this gene is autosomal recessive, its children may get sick because they are homozygotes of the mutation. So inbreeding will increase the risk of some autosomal recessive genetic diseases. Inbreeding coefficient (IF) refers to the probability of obtaining a pair of homozygous or identical genes from offspring through inbreeding. Couples who have a common ancestor in generations below their great-grandfather are considered close relatives. Cousin marriage is a relatively common consanguineous marriage. Most countries do not encourage consanguineous marriage, or even prohibit it. When close relatives get married, the mortality rate of offspring is high, and dementia, deformed children and genetic diseases often appear. This is because the husband and wife who get married by close relatives get more identical genes from the common ancestor, and the recessive harmful genes that are not conducive to survival are easy to meet in the offspring (that is, homozygous), so it is easy to give birth to children with poor quality. According to the estimation of the World Health Organization, everyone in the population carries about 5-6 recessive genetic diseases. In random marriage (non-consanguineous marriage), it is not easy to form homozygotes (patients) with recessive pathogenic genes because the husband and wife are not related by blood, have few identical genes and carry different recessive pathogenic genes. However, when close relatives get married, it is very likely that both husband and wife carry the same recessive pathogenic gene, so it is easy to meet in offspring, which will increase the incidence of genetic diseases in offspring. Therefore, the incidence of offspring of consanguineous marriage is as high as 70% to 80%, and offspring will suffer from genetic diseases.

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