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In Down syndrome, a person's cells have an extra copy of chromosome 21. In other words, instead of a pair of chromosomes, a person with Down syndrome has three of that chromosome. Down syndrome most often occurs when chromosomes fail to separate properly during meiosis. People with Down syndrome have a degree of mental retardation. Heart defects are also common, but can be treated.
In a trisomy syndrome, an extra chromosome is present so that the individual has three of a particular chromosome instead of the normal pair.
In Down syndrome, a person's cells have an extra copy of chromosome 21. In other words, instead of a pair of chromosomes, a person with down syndrome has three of that chromosome. Down syndrome most often occurs when chromosomes fail to separate properly during meiosis. People with down syndrome have a degree of mental retardation. Heart defects are also common, but can be treated.
In Down syndrome, a person's cells have an extra copy of chromosome 21. In other words, instead of a pair of chromosomes, a person with Down syndrome has three of that chromosome. Down syndrome most often occurs when chromosomes fail to separate properly during meiosis. People with Down syndrome have a degree of mental retardation. Heart defects are also common, but can be treated.
In Down syndrome, a person's cells have an extra copy of chromosome 21. In other words, instead of a pair of chromosomes, a person with down syndrome has three of that chromosome. Down syndrome most often occurs when chromosomes fail to separate properly during meiosis. People with down syndrome have a degree of mental retardation. Heart defects are also common, but can be treated.
Edwards' syndrome is caused by an extra (third) copy of chromosome 18. The extra chromosome is lethal for most babies born with this condition. It causes major physical abnormalities and severe mental retardation. Very few children afflicted with this syndrome survive beyond the first year.
No, that is false. Down Syndrome is also known as Trisomy-21. Monosomy is a condition where one chromosome is missing from what should be a pair in every cell throughout the body. Trisomy indicates a chromosome has three copies instead of a pair.
Down syndrome occurs because of the extra chromosome on chromosome 21. If you go onto google images and type in karyotype of Down syndrome, you will find a picture of the extra chromosome. Instead of having two chromosomes on chromosome 21, there is an extra. Type your answer here...
Because people who have Turner syndrome have one X chromosome instead of the two other females have. As they do not have a Y chromosome, they are female.
Usually humans have 46 chromosomes, divided into 23 pairs within each cell, one copied from each parent. Chromosome 21 is the smallest and the second human chromosome to be sequenced. Many genetic conditions are related to changes in particular genes on this chromosome including Cancers, Downs Syndrome and Alzheimer's Disease Changes in the structure in the number of copies of a chromosome may also cause problems with health and development. Cancer For example -translocation in chromosomes 12 and 21 have been linked to Lymphoblastic Leukemia whilst links between translocation of 8 and 21 Acute Myeloid leukemia. Downs Syndrome -a chromosomal condition that, in most cases is caused by trisomy 21 (each cell has 3 copies instead of the normal 2).
Down syndrome is usually caused by a condition known as Trisomy 21, which means that a person has three copies of Chromosome 21, rather than the usual two copies. An extra chromosome is added. The normal amount is 46, but people with Down syndrome have 47.Occasionally, the condition is a result of part of Chromosome 21 becoming fused to the end of another chromosome.More info on Chromosome 21While Chromosome 21 isn't the shortest chromosome, it is the one that contains the fewest genes (other than the Y chromosome). This is because genes on Chromosome 22 are more closely spaced, and thus the chromosome contains more genes, despite its smaller size.
Down's Syndrome is caused due to the presence of an extra 21st chromosome, resulting in 3 sets of 21st chromosome instead of just 2. This is because during Anaphase II of Meiosis II non-disjunction occurs and instead of one 21st chromosome going into each gamete, both go into one of the gametes and none goes into the other. When a normal gamete fuses with the gamete with an extra21st chromosome, it forms a zygote with 3 sets of 21st chromosome instead of 2 and that is known as Down's Syndrome.