Some time ago, a 5-year-old Chinese girl Rosie, who was adopted by an American couple, suddenly became popular on the Internet. Seeing her bright smile, you would never have guessed that this angel who fell down to earth was an abandoned “Tang baby” (Down’s Syndrome). Can you identify the “Down baby” in the picture? Down syndrome (21 – trisomy, congenital stupidity) British doctor Langdon Down first described the clinical features of the disease, in 1959, France’s Lejeune confirmed that the disease is associated with an extra G chromosome, later identified as chromosome 21. Clinical manifestations of Down’s syndrome: patients with severe mental retardation, small and rounded head, low and flat nose, small and externally upward slanting eye clefts, wide eye spacing, half-open mouth, tongue often stretched out of the mouth, and low ear position (the upper edges of the ears below the level of the eyes); short and thick necks, short fingers and toes, inwardly curved fingers, and one section of the pinky folds, which passes through the hand; proximal bowing of the bulb of the bunion, and the widening of the distance between the bunion and the second toe in the form of a “Straw foot”. It can often be accompanied by malformations of the reproductive organs, heart, digestive tract, and bones; immunity is low, and the incidence of acute leukemia is about 20 times higher than that of the average child. It usually does not survive to adulthood. According to the different karyotypes, Down’s syndrome can be divided into the following three categories: 1. Comprehensive Down’s syndrome: about 92.5% of all patients, the karyotype is “47, XX (XY),+21”, the main reason is that the father or mother formed gametes when the chromosome 21 does not segregate, so that a certain gametes have three chromosome 21, when this gamete is not separated, so that a certain gamete with three chromosome 21, and when this gametes with three chromosome 21, the father or mother can not separate. The main reason for this is the non-separation of chromosome 21 in the formation of gametes by either the father or the mother, resulting in a gamete with three chromosome 21s, and when this gamete is fertilized by another normal gamete, the developing individual has three chromosome 21s. Epidemiologic investigations have shown that the incidence of Down’s syndrome increases as the mother’s reproductive age increases. 2, translocation type Down syndrome: this type accounts for about 3% -4%, the patient increased a chromosome does not exist alone, but with a chromosome in group D or G Robertson translocation, the total number of chromosomes is 46, one of which is a translocation chromosome. The patient’s translocation chromosome, if inherited from a parent, with one of the two parents being a balanced translocation carrier with a karyotype of “45, XX(XY),-14,-21,+t(14q21q)”, will produce six gametes that will combine with normal gametes to produce six different offspring, of which 1/6 will be normal karyotypes and 1/6 are 14/21 translocation carriers, the remaining for monosomy or trisomy and abortion. 3, chimeric Down syndrome: about 1-2%, this type occurs because the normal fertilized egg in the early embryonic development of the process of cleavage, the 21st chromosome does not occur in the separation, the patient’s karyotype is often “46, XX (XY) / 47, XX (XY), +21”, and The severity of symptoms is determined by the proportion of “47,XX(XY),+21” cells, which is not as typical as in other Down’s syndromes. The incidence of Down’s babies in live births is about 1/800-1/600, and the condition is closely related to the mother’s gestational age. Not every child can be as lucky as Rosie, the little girl who was so full of genes, and every child is an angel and should not be given up. For children already born with the disease, their life expectancy depends more on the presence or absence of serious congenital heart disease, leukemia and resistance to infection, etc. Therefore, early intervention, regular medical checkups, and medication or surgical treatment are particularly important. In order to effectively avoid the birth of this kind of patients should pay attention to: 1, the right age to have children, the best age of childbearing: 21 ~ 30 years old; 2, do a good job of the couple’s pre-pregnancy eugenics examination; 3, for pregnant women over the age of 35 years old, under the age of 30 years old, pregnant women who have had a child with Down’s syndrome, one of the parents is a balanced translocation carrier or chimerism should be done before and after the pregnancy prenatal checkups; 4, before and after pregnancy, women of childbearing age should be avoided to receive large doses of radiation exposure; 5, do not just take medication or surgery. Women of childbearing age should avoid receiving large doses of radiation before and after pregnancy; 5, do not take chemical drugs casually; 6, prevent viral infections; 7, do a good job of prenatal screening and prenatal diagnosis.