Close relatives of three generations refer to oneself as the first generation, counting upwards from oneself, with parents as the second generation and grandparents and great grandparents as the third generation.
1、 What are the three generations of close relatives
1. Brothers and sisters who are related to their parents. Including full blood sisters of the same father and mother, half blood sisters of the same father and half blood. Although brothers and sisters with different parents are also called brothers and sisters in name, they are not related by blood.
2. The collateral relatives of grandparents and maternal grandparents, including uncles, aunts, nephews, nieces, uncles, aunts, nephews, and nieces.
3. Ancillary relatives of the same generation, including cousins sisters and sisters, who originate from grandparents.
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2、 The harm of consanguineous marriage
1. Leukemia
Offspring born to consanguineous couples are 13.5 times more likely to develop albinism and 63.5 times more likely to develop congenital ichthyosis than those born to non consanguineous couples.
2. Intellectual disability
The intellectual problems of children born to consanguineous marriages can also be affected to a certain extent. Generally, consanguineous marriages can easily lead to intellectual disabilities in children, and there are more cases of congenital abnormalities than children born to non consanguineous marriages.
3. Congenital malformation
Marriage between close relatives can have serious consequences. For example, couples who marry close relatives are likely to have offspring who die early, with a death probability more than three times that of children born to non close relatives. In addition, marriage between close relatives can greatly increase the rate of congenital malformations in children, and children born to close relatives are prone to congenital malformations, such as polydactyly or syndactyly.
4. Polygenic genetic disease
The likelihood of offspring from consanguineous marriages developing some polygenic diseases is much higher than that of offspring from non consanguineous marriages. The probability of offspring from consanguineous marriages developing polygenic diseases such as congenital heart disease or spinal cord fission is as high as 1.64%, while the probability of offspring from non consanguineous marriages developing these polygenic diseases is only 0.57%, which is much lower. In addition, the incidence of diseases such as hypertension, schizophrenia, cleft lip and palate is also relatively higher.