downs syndrome

[ann]

how does having an extra chromosome 21 cause all the characteristic symptoms of downs syndrome?

[MrSandman]

I believe it has do with recieving extra genes for the same trait. If you have two confliciting genes they will cause a mutation. Mutations almost always work out for the worst causing brain malfunction in a down's syndrome child. However, I think I should look this up again. Anyone want to add more please do.

[DrDNA]

Genes instruct the cell to make proteins which are needed in the correct amounts. For example, some genes make important proteins that instruct other genes to turn on and off at the right moment. These instructions need to be precise, accurate and sensitive. Having an extra chromosome is like driving a car with two drivers giving confusing instructions or you might look at it like adding too much of an ingredient to your stew, it may be edible, but it is not optimal.

Chromosome 21 is the smallest or one of the smallest. Most other chromosome duplications are lethal. Some x ory chromosome duplications are exceptions.

[MrSandman]

So I was right, DrDNA I'm going to construct a post on enzymes I like it if you would post on it.

[bio90]

Some x ory chromosome duplications are exceptions.

 

 

I think my teacher has discussed this with us before, I thought it was really interesting, but would like to know more about the implications of this mutation if you know more about it

[vampares]

No, there an extra chromatin making 21 a triplet. There's already two copies of every gene (hopefully). The mechanism that makes this happen is inherent to the chromosome itself. For some reason it's sticks and doesn't come apart properly. So when the eggs of the ovary are made, some are made correctly, others missing a 21 (not viable), others extra 21 (carrier) and others will be carriers but not have Down's.

 

The $64k is why on earth doesn't this disease phase itself out?

 

You do the math. You do the worrying. You pay the bills. You take the stigma. You get the picture. Corky gets his own heroic TV show and a vacation in the Caribean Isles.

 

I think that this is like most other genetic conditions that produce a generalized dymorphia. Fetal development depends on rapid growth. The slow production of a critical protein leads to disproportionate cell division. The resulting frame upon which a person then starts their life may well be their undoing. I don't know if there are any other issues arising from Down's. If there were I would expect more drugs. Tom Ridge might have Down's.

[Psycho]

No, there an extra chromatin making 21 a triplet. There's already two copies of every gene (hopefully). The mechanism that makes this happen is inherent to the chromosome itself. For some reason it's sticks and doesn't come apart properly. So when the eggs of the ovary are made, some are made correctly, others missing a 21 (not viable), others extra 21 (carrier) and others will be carriers but not have Down's.

 

The $64k is why on earth doesn't this disease phase itself out?

 

Because it isn't an inherited disorder, it is due to an imperfection in meiosis creating a gamete with an extra chromosome 21, it could occur at any time to anyone. Due to chromosome 21's small nature it means viable offspring can still occur whereas with larger chromosomes they have to0 many genes controlling too many functions that the offspring can't survive.

 

Other problems can occur with multiple X chromosomes such as Poly X syndrome or Klienfelters syndrome.