What gene and chromosome does Down syndrome affect?

Answer 1

Three to four percent of all cases of trisomy 21 are due to Robertsonian Translocation. In this case, two breaks occur in separate chromosomes, usually the 14th and 21st chromosomes. There is rearrangement of the genetic material so that some of the 14th chromosome is replaced by extra 21st chromosome. So while the number of chromosomes remain normal, there is a triplication of the 21st chromosome material. Some of these children may only have triplication of part of the 21st chromosome instead of the whole chromosome, which is called a partial trisomy 21. Translocations resulting in trisomy 21 may be inherited, so it's important to check the chromosomes of the parents in these cases to see if either may be a "carrier."

The remainder of cases of trisomy 21 are due to mosaicism. These people have a mixture of cell lines, some of which have a normal set of chromosomes and others which have trisomy 21. In cellular mosaicism, the mixture is seen in different cells of the same type. In tissue mosaicism, one set of cells, such as all blood cells, may have normal chromosomes, and another type, such as all skin cells, may have trisomy 21.


The 21st Chromosome and Down Syndrome

The chromosomes are holders of the genes, those bits of DNA that direct the production of a wide array of materials the body needs. This direction by the gene is called the gene's "expression." In trisomy 21, the presence of an extra set of genes leads to overexpression of the involved genes, leading to increased production of certain products. For most genes, their overexpression has little effect due to the body's regulating mechanisms of genes and their products. But the genes that cause Down syndrome appear to be exceptions.

Which genes are involved? That's been the question researchers have asked ever since the third 21st chromosome was found. From years of research, one popular theory stated that only a small portion of the 21st chromosome actually needed to be triplicated to get the effects seen in Down syndrome; this was called the Down Syndrome Critical Region. However, this region is not one small isolated spot, but most likely several areas that are not necessarily side by side. The 21st chromosome may actually hold 200 to 250 genes (being the smallest chromosome in the body in terms of total number of genes); but it's estimated that only a small percentage of those may eventually be involved in producing the features of Down syndrome. Right now, the question of which genes do what is highly speculative. However, there are some suspects.

Answer 2

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What gene and chromosome does Down syndrome affect?

Answer 3

The 21st Chromosome is affected.
Down syndrome is a genetic disorder caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British doctor who described it in 1866. The condition is characterized by a combination of major and minor differences in body structure. Often Down syndrome is associated with some impairment of cognitive ability and physical growth as well as facial appearance. Down syndrome is usually identified at birth.

Answer 4

I want to believe that down syndrome is caused by a mutation of the 21 chromosome if you are viewing a carotype.

Answer 5

The gene and chromosome defects cause Down Syndrome, not the other way around as your question might imply. Having the right order of things helps to understand evolution and biological processes.

Answer 6

Yes, there is no gene for Down Syndrome. It is caused by an extra chromosome that is fertilized and grows in the embryo. Thus the offspring is mentaly retarded, short in statute, round face. If under 30,1-1,500 births have down syndrome. ir over, chances double.

Answer 7

there is no gene related. it is caused by the trisomy of chromosome21 in human beings ie instead of 2 there are 3 chrmosomes containing the similar alleles