Down syndrome is a genetic disease where there is an extra chromosome on the 21st chromosome. Now there are three types of Down syndrome Trisomy 21, Mosaic Down syndrome, and Translocation Down syndrome. First we’ll talk about Trisomy 21. According to Mayo Clinic Staff (2011) “More than 90 percent of the time, Down syndrome is caused by trisomy 21. A child with trisomy 21 has three copies of chromosome 21 — instead of the usual two copies — in all of his or her cells.”(Para.3) so from this we can conclude that this is the most common type of 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.
The syndrome occurs in all races and equally between both males and females however it is not inherited in 99% of cases. Prader-Willi Syndrome is rare with only 1 in 20,000 people born with the mutation. Normally offspring inherit one copy of chromosome 15 from their mother and another from their father, however in patients diagnosed with Prader-Willi Syndrome some of the genes on chromosome 15 are missing. The mutation is caused by lack of active genetic material in the region of chromosome 15 that affects Prader-Willi Syndrome (15q11- q13). There are three possible mutations to cause this inactivity.
Down's Syndrome Down's syndrome is a genetic condition involving an extra chromosome, this change occurs around the time of conception. A person with Down's syndrome has forty-seven chromosomes instead of the usual forty-six. A relatively common genetic disorder, Down's strikes 1 out of 600 babies. In 95 percent of all cases, the disorder originates with the egg, not the sperm, and the only known risk factor is advanced maternal age-at age 35, a woman has 1 chance in 117 of having a baby with Down's; at 40, her odds are 1 in 34. (Graves, 1990) People with Down's syndrome all have a certain degree of learning disability .
Down syndrome, also known as trisomy 21, occurs when a child is born with three copies chromosome 21, as you can see in Figure 1. This can be caused by three different processes; nondisjunction, mosaicism, or translocation. Nondisjunction occurs during the reduction of chromosomes, from 46 to 23, after the egg and sperm have combined, causing one parent to pass on 24 instead of 23. In the case of Down syndrome, the extra chromosome is chromosome 21. Mosaicism is a rare occurrence, happening “in approximately one to two percent of Down syndrome cases” (Johnson, 2013).
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.
According to the National Down Syndrome Society (NDSS), “one in every 691 babies born in the United States is born with down syndrome, making it the most common genetic disorder.” A person with this genetic defect tend to have delays in regards to physical growth, have a particular set of physical structures—particularly facial ones—, and have a moderate to severe intellectual impairment. There are several physical structures that are typical of someone with down syndrome. As said on the wikipedia page concerning down syndrome, they are namely: “abnormally small chin, oblique eye fissures on the inner corner of the...
What is the impact it has on society? First, Down syndrome, also called trisomy 21, is a condition in which the number of chromosomes the human cells contain is more or less than 23 pairs which causes a delay in the way a child develops mentally and physically. Down syndrome is the most commonly occurring genetic disorder. There are three types of Down syndrome: trisomy 21 accounts for 95% of cases, translocation accounts for about 4% and mosaicism accounts for about 1%. Actually, according to some researchers recently done in the USA, one in every 691 babies is bor... ... middle of paper ... ... and terribly sad.
Some investigators reported that older fathers may also be at an increased risk of having a child with Down syndrome. It is well known that the extra chromosome in trisomy 21 could either originate in the mother or the father. Most often, however, the extra chromosome is coming from the mother. Description People with Down syndrome are first and foremost human beings who have recognizable physical characteristics and limited intellectual endowment which are due to the presence of an extra chromosome 21. The estimated incidence of Down syndrome is between 1 in 1,000 to 1 in 1,100 live births.
Down syndrome is named after John Langdon Down, a british physician who wrote about the syndrome in 1866. It is also the most common chromosome abnormality in humans. In the United States alone, about around 1 in 700 children are born with it. It is unknown why it occurs. It is, however, known what increases the probability of it happening.