Doctor insights on:
What Type Of Mutation Causes Down Syndrome
In genetics, a mutation is a change in the nucleotide sequence of the genome of an organism, virus, or extrachromosomal genetic element. Mutations result from unrepaired damage to dna or to RNA genomes (typically caused by radiation or chemical mutagens), from errors in the process of replication, or from the insertion or deletion of segments of dna ...Read more
Not mutation, number: Down syndrome is an abnormality of chromosome numbers, not a trait or mutation in the gene code. During conception only one of chromosome of each pair is given by both parents to the fertile egg. If a parent adds their 2 nbr 21chm to the other parents nbr 21, 3 end up in the egg ; the excess 21 causes the all the problems. Rare forms are causes by a extra piece of a 21, but that's another issue. ...Read moreSee 1 more doctor answer
Is there a type of mosaic Down syndrome that doesn't require the mutation to come from either parent to have a downs child?
Yes: A mosaic Down syndrome child can come from a normal egg and normal sperm, produced by normal parents. The fertilized egg would start out normal with 46 chromosomes. It can divide into 2 normal cells, which themselves divide again. If on one of the early divisions, one cell ends up with an extra #21 chromosome and survives to continue dividing, the child will be mosaic with some trisomy 21 cells. ...Read moreSee 1 more doctor answer
Separate study: If you are having the one study done it is simple enough to arrange for the other study at the same time. They are separate tests and often done at a separate lab. ...Read more
Extra chromosome 21: A woman's chances of giving birth to a child with Down syndrome increase with age because older eggs have a greater risk of improper chromosome division. By age 35, a woman's risk of conceiving a child with Down syndrome is 1 in 400. By age 45, the risk is 1 in 35. However, most children with Down syndrome are actually born to women under age 35 because younger women have far more babies. ...Read moreSee 1 more doctor answer
Several possible: The features of Down syndrome are dependent on the addition of one extra segment of a 21 chromosome which is more likely as women age. You can get this several ways. The traditional DS (~95%) has 3 copies of a 21 chromosome. About 4% have the specific extra 21 piece stuck on a regular chromosome (trans-location).About 1% have a mosaic of some normal and some 21 trisomy in variable amounts. ...Read moreSee 2 more doctor answers
Chromosome influence: The size and shape of the skull and facial features of Down syndrome patients is heavily influenced by the effect of the extra chromosome present in every cell of the body. The same goes for eyes, hands, feet, all of which require a lot of decoding during formation to produce the structures. Other chromosome defects produce some common features to those born with a specified extra chromosome. ...Read moreSee 1 more doctor answer
Hi, a quick question, I have a six week old niece, when she was born there was worries she was down syndrome, she got all the tests and thank god they came back clear, my question is could the tests have been wrong, cause there is times you look at her a
Test limits: I will assume that the tests that were completed was specific to look for a chromosomal abnormality. The typical ds diagnosis can be ruled out, but the test does not exclude other problems that can give an infant an unusual look, or might be a problem in the future. The pcp can monitor the situation over time & look for other issues if there appears to be a need for additional study. ...Read moreSee 1 more doctor answer
Extra chromosome mtl: The traditional ds patient has an extra 21 chromosome (c) that resulted from an improper splitting of the c pairs as the egg is being formed. At conception dad's 21 is added to the pair already there, while all the other chromosomes just have a pair. Cell division from conception will place the triplet 21 in every cell of the body, and the imbalance of the material leads to the features of ds. ...Read more
DNA defects: Chromosome 21 seems to be the cause. Two most common types are trisomy 21 where ther is an entire extra chromosome in each cell. The other is translocation where only an extra piece of the chromosome is found. It can be an isolated defect or an inherited defect. Rare exotic forms include polyploidy and haploid forms and chimeras. Sorry you asked? ...Read moreSee 1 more doctor answer
Selection variables: If a woman generates an egg that contains 2 rather than 1 chromosome 21's, the addition of a 21 from the sperm will cause the trisomy 21 condition. Some of these miscarry & some deliver. When males generate a sperm that carries irregular information, there is speculation that the ones with bad information do not swim as well & thus can't pass the defect. ...Read more
Poor health: The expected lifespan of a ds patient born today exceeds 60 years if they have access to the basic medical care & dietary resources of average individuals. They do have higher risks for a variety of health issues involving their glands (thyroid, diabetes) their bones (scoliosis, joint pain & weakness) and the impact of obesity is much worse for their overall health. ...Read more
Other way around: Atrioventricular (av) canal defect is a relatively common congenital heart defect in children born with down syndrome. Down syndrome "causes" av canal defects, not the other way around. Av canal defect is a major congenital anomaly with the potential to cause severe symptoms. However, in most cases, av canal defect can be repaired. High levels of surgical skill is important for best outcomes. ...Read moreSee 1 more doctor answer
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