-
Close relatives (or kinship) refer to ancestors who have the same ancestry within three generations. If they marry, it is called consanguineous marriage. Couples who are closely related may get the same genes from their ancestors and pass them 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.
——————————————————————————————————————————
In genetic counseling, the most common questions about consanguineous marriage mainly include the following three types:
1. How to judge which generation of close relatives get married?
Starting from the same generation, it is the first generation, and so on. If cousins get married, grandma belongs to the first generation, mother belongs to the second generation, and the combination of cousins is the third generation. China's marriage law stipulates that blood relatives are forbidden to get married within three generations.
2. What is the risk of consanguineous marriage?
The coefficient of consanguineous marriage listed in the above table is its genetic risk. For diseases with low incidence, such as albinism, this risk rate is generally higher than that of random marriage; If it is a disease with high incidence, such as thalassemia or bean diseases in southern China, the risk brought by this kind of consanguineous marriage is not necessarily higher than that brought by local people's random marriage.
3. When one party is a descendant of a close relative, can you marry him?
Although they are descendants of consanguineous marriage, they should not worry about the consequences of consanguineous marriage after marrying other non-consanguineous spouses if their families and themselves have no obvious history of genetic diseases. In other words, there is no obvious difference between the influence on offspring and normal marriage.