Down Syndrome is also (or formally) known as mongolism, and is the most frequent chromosomal abnormality in the United States. Over 350,000 people carry this condition. It is caused by an extra 21st chromosome. This is also known as trisomy 21. Instead of 46 chromosomes in each cell it was determined that an extra 21st chromosome affected Down syndrome, this occurs 95% of the time.
The change in the gene is an occurrence that happens only by chance in which researchers believe affects a single sperm or egg just before conception. However, for parents that have already had a child with Progeria, they are more likely to have a second children with the disease. This is because of a condition called mosaicism where a parent has the genetic mutation for Progeria in a very small proportion of their cells, but they do not actually have Progeria (“Progeria101/FAQ”). Moreover, a child with Progeria typically will look normal at birth... ... middle of paper ... ...at was used in the first trial was named the first-ever treatment for Progeria (“Progeria 101/faq”). In conclusion, Hutchinson-Gilford Progeria Syndrome or Progeria, is a rare and fatal disease that occurs in children.
Trisomy 21 is the most common type of Down syndrome. About 92% of Down syndrome patients have this type. People with Trisomy usually have physical problems. Mosaic Trisomy 21 happens when an egg or sperm come in with an extra copy of chromosome 21, then, once an embryo is formed and starts to develop, the chromosome is replicated in some of the cells. In Mosaic some cells have a normal number of chromosomes and some have an extra chromosome 21.
The type of mutation that occurs in Down syndrome is aneuploidy that is the irregular number of chromosomes in a cell. The most common of the three is the trisomy 21 that occurs in about 90% of people with the disorder. In this factor the human is given three copies of the chromosome 21 instead of the common two copies. This occurs due to the complications of the cell division in the process of the egg or sperm. The next case is mosaic which happen when there are inequality of cells with three copies of chromosome 21 and others with the original two copies.
Rarely is it inherited, Down syndrome is caused by three types of chromosomal abnormalities: Trisomy 21, Mosaic Down syndrome, and Translocation Down syndrome. The most common variation, Trisomy 21, occurs in about 95% of cases. According to “Down Syndrome”, this common variation is caused by “an error during the formation of the egg or sperm” and results in “either one having an extra chromosome.” After the sperm and egg mate, the cells produced will have three copies of chromosome 21. In addition, Mosaic Down syndrome, which accounts for 3% of cases, leads to some cells being affected with three copies of chromosome 21, with others unaffected. Finally, Translocation Down syndrome results 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” (“Facts about Down Syndrome”).
Trisomy 21 is the most common type of down syndrome and it account for 95% of cases. When someone has trisomy 21 they have 47 chromosomes instead of 46 in every cell, which is caused by an error in cell division known as nondisjunction. Usually a baby inherits genetic information from both parents, 23 from each parent, but at some point during cell division a pair of 21st chromosomes in either the X or Y chromosome fails to separate, causing the child to have an extra 21st chromosome. This one extra chromosome is the cause of down syndrome’s development delays and physical features that are associated with down syndrome. Translocation down syndrome accounts for about 3% of cas... ... middle of paper ... ...hat conceive over the age of 35 and older are most likely to have a child with the condition.
Down Syndrome in Children Down syndrome is one of the most common and easily recognized genetic disorders. It is caused by abnormal cell division that involves the 21st chromosome pair of the 23 pairs of chromosome found in all normal human cells. There are three types of these abnormalities, which are non-disjunction, translocation, and mosaicism. Ninety five percent of children born with Down syndrome are a non-disjunction type which is three rather than two chromosome 21s. About three to four percent of cases are because of translocation which is chromosome 21 detaches and attaches to another chromosome.
Roger W. Harms, a medical doctor, states, “Human cells normally contain twenty-three pairs of chromosomes. One pair comes from your father and one pair comes from your mother.” In each pair, one chromosome comes from the father, and one comes from the mother. One of the three genetic variations that can cause Down Syndrome is Trisomy 21. This version of Down Syndrome occurs more than 90% of the time. It re... ... middle of paper ... ...egative impact on the family, the favorable effect it has outweighs the harmful influence.
The estimated incidence of Down syndrome is between 1 in 1,000 to 1 in 1,100 live births. Each year approximately 3,000 to 5,000 children are born with this chromosome disorder. It is believed there are about 250,000 families in the United States who are affected by Down syndrome. The vast majority of children with Down syndrome (approximately 95 percent) have an extra 21 chromosome. Instead of the normal number of 46 chromosomes in eachcell, the individual with Down syndrome has 47 chromosomes.
There are three possible mutations to cause this inactivity. The most common cause is the deletion of the part of chromosome 15 that is inherited from the father, occurring in 70% of cases. In 25% of cases uniparental disomy (UPD) occurs and two copies of the chromosome are received from the father and none from the mother. 5% of patients diagnosed with Prader-Willi syndrome have an ‘imprinting mutation’. This is a form of translocation and means that the sequences of the genes on chromosome 15 are altered.