Down Syndrome, a chromosome abnormality is present in all ethnicity, social economic classes, and gender which is defined as a "congenital disorder by an extra chromosome on the chromosome 21 pair." Although there are many theories that have been developed for the cause of chromosome abnormalities, it is still not known what actually causes Down syndrome.Down syndrome was discovered and named after a British physician called John Langdon Haydon Down who first studied it in 1866. At first it was called Mongolism because Down syndrome people have some physical features that look like Mongolian.The affected individuals have upward slanting eyes, a fold of skin that starts at the inner corner ...view middle of the document...
This method, however, occurs in the ovaries and testicles.Down syndrome is a chromosomal disorder occurred by the presence of an extra #21 chromosome. Instead of having 46 chromosomes in each of his/her cells, a person with Down syndrome has 47. The extra chromosome may be received from either the egg or the sperm. During cell division in meiosis of a sperm or egg, the two #21 chromosomes do not separate properly (nondisjunction). This abnormal gamete will have an extra #21 chromosome which later, if united with a normal germ cell which has one #21 chromosome, may lead to trisomy 21. The first cell at conception then has 47 chromosomes instead of "normal set" of 46 chromosomes. When this three #21 chromosomes cell continues to multiply, and the pregnancy is carried to term, a baby with Down syndrome will be born.There are two more ways this genetic problem may occur. The second one is called Tranloscation which happens when the extra 21 chromosome attaches itself to another chromosome. The chromosomes affected in this case are usually 14, 21, or 22. occurs when one of the parents is a carrier of translocation ( the balanced carrier). This type of chromosome error is found in about 4 percent of individuals with Down syndrome.The third and least common chromosome deficiency is called mosaicism. This is found in only 1 percent of individuals with Down syndrome . Mosaicism occurs when there is an extra 21 chromosome on some cells but not on others. One of the causes of mosaicism could be an error in cell division soon after conception.The risk actually also varies with the age of the mother. The incidence of Down syndrome in children born to 25-year-old mothers is approximately 1 in 1200; the risk increases to approximately 1 in 350 for 35-year-olds and approximately 1 in 120 for women older than 40 years.Down syndrome is the most commonly occurring genetic condition in the world. The estimated incidence of Down syndrome is between 1 in 800 to 1 in 1,100 live births. Each year approximately 3,000 to 5,000 children are born with this disorder. It is believed there are about 250,000 families in the United States who are affected with Down syndrome.There is no cure for Down syndrome. Nowadays there are several types of prenatal tests to detect Down syndrome.Screening Tests: Screening tests are used to look for potential problems and to identify those who have high risk of having a genetic disordered baby.The triple screen, the alpha-fetoprotein plus, and the quad test measure the amounts of certain hormones and proteins in the blood. The results of these tests together with the woman's age, will provide an estimate of her risk of having a child with Down syndrome. These tests are performed between the fourteenth and sixteenth week of gestation. Most of fetuses with Down syndrome can be identified by considering the mother's age and employing these screening tests.In addition to those, ultrasound examinations are almost always performed. During...
