What is chromosome examination? Chromosome examination is performed by incubating peripheral blood in a 37°C incubator for 72 hours under the action of PHA, a cell growth stimulating factor, and adding colchicine to stop the cells at mid-cytokinesis to facilitate observation. and stained with G to show bands. The collection can then be observed under the microscope for karyotype analysis. The human normal karyotype has 23 pairs of chromosomes, 22 of which are autosomes and one pair of sex chromosomes, X and Y, respectively. The female pair is 46,XX and the male pair is 46,XY. The normal karyotype of female is 46,XX; 2. The normal karyotype of male is 46,XY. Indications of chromosome examination Significance of chromosome examination and danger of abnormalities Chromosome G banding technique can detect chromosome number abnormalities and structural abnormalities as well as deletion, duplication and inversion. It is used clinically to analyze the causes of infertility, infertility and recurrent miscarriage, to reduce the risk of recurrence of genetic diseases in the family line, to avoid the transmission of serious harmful genes to offspring, to provide eugenic guidance for marriage and childbirth, to reduce birth defects and to improve the success rate of assisted reproduction techniques. Trisomy 21 1, Down syndrome is also known as “trisomy 21” is one of the most common serious birth defects, most of which are caused by the phenomenon of the 21st non-separation of the mother’s egg. 2, incidence: the incidence of newborns up to about 1/600-1/800, more males than females, the age of the mother is an important factor affecting the incidence. 3, clinical manifestations: low weight and length at birth, hypotonia, prominent craniofacial deformities, small and round head, round and flat face, flat nose, wide eye spacing, often strabismus, two external eye angles upward, tongue outward, small ears, auricular deformities, short and wide back of the neck, the affected child has short limbs, wide and fat hands, through the hands. 4. About 1/2 or more patients have congenital heart disease, gastrointestinal malformation (such as duodenal stenosis), males have not been seen to have children, a few female patients can have children, developmental delay and mental retardation are the most prominent and serious manifestations of the disease. Karyotype of trisomy 21 1, most of the trisomy 21 is standard, accounting for 95% of all cases with severe disease. 2. The karyotype is: 47, XY, (or XX), +21. 3. The cause of pathogenesis: 95% of the cases occur in mothers with chromosomal non-segregation and mainly in the first meiosis. Only a very small percentage of typical trisomy 21 is inherited, i.e., the mother is the patient of the disease. Prevention of trisomy 21 1. Prenatal testing should be done for pregnant women over 35 years of age, pregnant women under 30 years of age but who have given birth to a child with a high risk rate of Down syndrome, or those with one of the two parents being a balanced translocation carrier or chimeric. 2.Women under 30 years old who have given birth to a child with the disease and their first-degree relatives who have the disease or have a balanced translocation carrier should have chromosome examination. 3.Checking method: take the amniotic fluid cells of pregnant women at 16~20 weeks or chorionic villus cells at 9~12 weeks for chromosome examination. Note 1.Chromosome examination usually draws peripheral blood lymph for cell culture without strict fasting, and blood can be drawn normally for chromosome examination during menstruation. 2.Enhance nutrition, maintain good sleep and avoid straining. 3.When taking drugs that inhibit lymphocyte growth, you should come to the hospital two weeks after stopping the drugs to have blood tests, because the chromosome examination technique is mainly to culture the lymphocytes in the blood. Avoid taking drugs to inhibit cell growth, which leads to a low number of cells and is not conducive to karyotype analysis.