• Down syndrome (trisomy 21)
  • Mahya Badbarouni,1,*
    1. student of islsmic azad university of Dezful


  • Introduction: Down syndrome is known as trisomy 21, a condition in which people have 47 chromosomes per cell instead of 46 per cell. Trisomy 21 is caused by an error in cell division. This extra chromosome occurs randomly and is dependent on the mother's age. Basically, the older the mother is, the higher the chance of it occurring in the fetus. But the interesting thing here is that most of the affected children are born to mothers under 35 years old because the number of children born to these mothers is more than that of mothers over 35 years old in the society. The incidence of Down syndrome is estimated to be between 1 in 1,000 and 1 in 1,100 live births worldwide. Characteristics of children with Down syndrome: Distinctive features such as flat face, small ears, slanted eyes and small mouth, short hands and feet Loose joints. Below average intelligence Many children with Down syndrome are also born with heart, intestinal, ear or breathing problems. These health conditions often lead to other problems, such as respiratory tract infections or hearing loss. But most of these problems can be treated. Impulsive behaviors. Weak analysis power. Mental retardation. Low learning bias. Short attention span. Obsessive distraction Treatment: There is no definite treatment for it. But it must be acknowledged that early intervention, high quality health care, good educational opportunities, proper nutrition and many other interventions make a big difference in a person's life. According to research, if the mother's gestational age is older than 35 years, the probability of the baby's Down syndrome increases. Also, if they have previously given birth to a child with Down syndrome, the probability of having a new child increases. Sometimes it is seen that the parents' genes are equal, but one of those genes is not in the right place. The mother or father may not have this disease themselves, however, it is possible that their child will have one of the types of Down syndrome. Trisomy 21 This model is the most common type of Down syndrome in the fetus, in which each individual cell receives three copies of chromosome 21 instead of two. Translocation Down syndrome In the previous model, a separate copy was created from chromosome 21. But in this model, the extra chromosome sticks to the previous chromosome 21. As a result, the number of chromosomes remains the same as 46 Mosaic Down syndrome This type can be considered the rarest model of this disease in which only some cells have an extra chromosome. Therefore, the symptoms of Down syndrome are much less common in these people prevention: Sonography of N.T Between the 11th and 14th week, using ultrasound, they check the fold on the back of the fetus's neck. Triplicate experiments Between weeks 15 and 18, the mother's blood should be checked with some tests and the desired factors should be measured. Combination test This test combines the screening results of the first 3 months of pregnancy, blood tests and NT ultrasound with the quadruple screening of the second 3 months. DNA testing This test is performed without cells and in which the genetic material and DNA present in the mother's blood are analyzed Genetic ultrasound Between 18 and 20 weeks of the fetus, the doctor must combine the results of the blood test with the result of a very accurate ultrasound and examine the details. Diagnostic tests: sampling of placental villi. amniocentesis Subcutaneous umbilical cord blood sampling Improving people's lives through: occupational therapy, speech therapy and physiotherapy. Enrollment in special schools. There is no conclusive scientific research that shows that Down syndrome is caused by environmental factors or parental activities before or during pregnancy All 3 types of Down syndrome are genetic disorders (related to genes). But only 1% of all cases of Down syndrome have a hereditary component, meaning they are passed from parent to child through genes.
  • Methods: by study and reviwe simmilar articles
  • Results: By performing screening tests and diagnostic tests, it is possible to prevent the birth of genetically defective babies.
  • Conclusion: It is a genetic disease that is caused by the presence of an extra copy of chromosome 21. It causes symptoms such as: small nose, upper eyelid slits, short stature, mental disability in them. Heart problems are seen in half of them. There is no treatment for the disease and it is before birth. The baby should undergo diagnostic tests for prevention.
  • Keywords: Trisomy 21. Down syndrome. Genetics. Chromosome. DNA