Myth #1 Healthy people don’t give birth to children with genetic diseases Do healthy people give birth to children without genetic diseases? Actually, no. For example, in the case of autosomal recessive genetic disorders, those who are normal in appearance are likely to be carriers of a genetic disorder and pass it on to future generations. In the case of autosomal recessive disorders, for example, a carrier of a mutation in a disease-causing gene will not have clinical symptoms because the mutated disease-causing gene and its corresponding chromosomal allele are normal, and the malfunction of the disease-causing gene is “compensated” or “masked” by the normal gene. “The clinical manifestation is “normal”. However, when both partners are carriers of an autosomal recessive disorder, there is a high probability of having a child with the genetic disorder. In Guangdong Province, for example, the most common form of thalassemia is thalassemia, with a carrier rate of 14% and an incidence rate of 7.8% (data from China News Network), which means that, in terms of probability, 14 out of 100 people are carriers of the thalassemia gene mutation and 7 out of 100 people are thalassemia patients. The diagram below shows the inheritance and pathogenesis of autosomal recessive disorders. As you can see, a couple with a carrier of the land poverty has a 1/4 chance of having a child with land poverty, a 1/4 chance of having a completely normal offspring, and a 2/4 concept of having a carrier of land poverty just like the parents. Myth 2: If there is no history of genetic disease in the family, the offspring will not have genetic disease. Genetic diseases are not always inherited from the previous generation, but can also be caused by de novo mutation of genetic material during the formation of germ cells or the division of fertilized eggs. Congenital dysgenesis occurs mainly due to the non-separation of chromosome 21 in the germ cells of one of the parents during meiosis to form gametes, or in the fertilized egg during mitosis. Since most children with monosomy are not viable, only trisomic offspring are usually born. The pathogenesis of trisomy 21 is mostly related to the aging of the egg cells due to the advanced age of the mother, and only rarely is it familial (i.e., one of the parents is congenitally stupid). Since males with congenital dysgenesis are unable to have children, there is no question of inheritance from the offspring. Myth 3 Genetic diseases are passed from generation to generation and cannot be avoided or treated In reality, some people believe that as long as there is a member or history of a genetic disease in the family, it will be passed from generation to generation and are therefore pessimistic and desperate. Genetics has evolved from a simple understanding of genetic diseases in the beginning to today, with the development of modern medical technology, more and more genetic diseases can be detected before birth, that is, prevented, and in some cases, even therapeutic interventions can be made to achieve relief of symptoms, improve the quality of life of the affected child and prolong life expectancy. Nowadays, common congenital genetic disorders such as congenital hypothyroidism, phenylketonuria, silkworm disease (G-6PD deficiency) and congenital adrenal cortical hyperplasia have been included in free newborn screening programs in some regions; many regions have also become specialized prenatal diagnosis centers, which can carry out prenatal diagnosis of common monogenic genetic disorders and chromosomal disorders, so that they can be prevented in advance. This can prevent the birth of children with congenital genetic diseases and improve the quality of the population at birth.