I think that having an extra chromosome 21 is tolerable to the point that someone with this condition can survive to maturity because it does not replicate.
There should only be a pair of chromosome 21. In the event that there are 3 chromosome 21, the person that has this extra chromosome has Down syndrome. Changes in the number and structure of this chromosome may result to delayed development, intellectual disability, but not immediate death.
Yes, of course! They may not always realize that instead of helping sometimes they're harming. They could push their child into a school that can help them for the future even though they want to try a different school. They can annoy their child and they'll get sick of it and lose interest in their subject.
Mitosis determines the traits presented in the cluster of cells.
