Detailed Instructions: Given a passage and a query based on the passage, generate an unambiguous, concise and simple answer to the query from information in the passage. Note that the answer may not be present in exact form.
Problem:Also, because Down's syndrome is present from the time of conception, nothing a woman does in pregnancy will influence whether or not her baby has Down's syndrome. Nothing is known which could have stopped the parent giving an extra chromosome. While similar to simple trisomy 21, the difference is that the extra chromosome 21 is present in some, but not all cells, of the individual. This type of Down syndrome is caused by abnormal cell division after fertilization. The name comes from a random order of normal and abnormal cells (a mosaic). Although translocation Down syndrome occurs via a different mechanism than trisomy 21, the physical and features that mark the condition are the same. Mosaic Down Syndrome In mosaic Down syndrome, not all cells in the body have 46 chromosomes. Translocation Down syndrome: This type accounts for a small percentage of people with Down syndrome (about 3%). 2 This occurs when an extra part or a whole extra chromosome 21 is present, but it is attached or “trans-located” to a different chromosome rather than being a separate chromosome 21. References: 1  Coleman, Mary and Rogers, PT. Medical Care in Down Syndrome: A Preventative Medicine Approach. 2  Korenberg, JR et al. Down syndrome phenotypes: The consequences of chromosomal imbalance. 3  Patterson, D. The integrated map of human chromosome 21. In Etiology and Pathogenesis of Down Syndrome, Wiley-Liss, 1995, p 43-55. Additional NIH Resources (2 links) 1  National Human Genome Research Institute: Chromosome Abnormalities. 2  National Human Genome Research Institute: Down Syndrome Research Expedited by Decoding of Human Chromosome 21 - Second Human Chromosome Sequenced by the Human Genome Project (May 2000) Like trisomy 21, mosaic Down syndrome is not inherited. It occurs as a random event during cell division early in fetal development. As a result, some of the body's cells have the usual two copies of chromosome 21, and other cells have three copies of this chromosome. responsible for only one to two percent of cases with Down syndrome. Translocation, the third form, occurs in only three to four percent of people with Down syndrome. In translocation, a piece of chromosome or a whole chromosome breaks off during meiosis and attaches itself to another chromosome. The presence of an extra part of the number 21 chromosome causes the features of Down syndrome. Although most cases are the result of random events, the risk of recurrence may be greater for The most common type of unbalanced translocation is translocation Down syndrome. Translocation Down syndrome produces the same symptoms and physical characteristics of regular Down syndrome. In the translocation type of Down syndrome, the child has three copies of the long arm of chromosome 21 instead of two. The chromosomes of parents of a child with Down Syndrome caused by a translocation are studied to see whether the translocation was inherited. What is the treatment for Down syndrome? Treatment for Down syndrome is based on the person's physical problems and intellectual challenges. Query: how does translocation of down syndrome occur
Solution:
Translocation of down syndrome occurs when extra chromosome 21 is present, but it is attached or “trans-located” to a different chromosome rather than being a separate chromosome 21.