Downs Syndrome - Trisomy 21?

[Makubex]

I've understood it like this; When a person is suffering from Downs Syndrome, with the version Trisomy 21, the person has got 47 Chromosomes instead of the 46. 23 from each parent, makes it 23 chromosome pairs, but the 47th one disturbs the balance? But if the person instead had gotten two extra chromosomes he would have been brighter then normal people, with 1 extra from each parent, and he would have had 24 chromosome pairs. I guess it's much more complicated, but am I totally wrong, or am I a bit on the right track?

[James]

Most trisomies are lethal. Having extra chromosomes is not good and wouldn't make you 'brighter'. You would likely be unviable. Do some research on aneuploidy.

[Makubex]

But the we would be brighter, in theory, if we could make our bodies able to withhold more chromosomes and use them instead of taking damage from them?

[James]

The number of chromosomes an organism has does not determine how 'bright' is it.

[MrMistery]

The number of chormosomes in an organism is the result of millenia of evolution. The human karyotipe is very stable, and works best with 46 chromosomes. If you happen to get an extra chromosome, you usually die young or die in the woumb, even before you are born. There are notable exceptions to this. If the extra chromosome is from pairs 21,18,13, or the X or Y chromosomes, you will live, however have a genetic desease: trisomy 21(down syndrome), trisomy 18(eduards syndrome), trisomy 13(patau syndrome), XXY(Kleinefelter syndrome) or XYY(doesn't have a name).
If however you happen to receive two extra chromosomes, you will surely die. This can be happen in 2 ways actually: if the chromosomes are from the same pair it is called a tetrasomy. If the chromosomes are from different pairs it is called a double trisomy. In humans it doesn't really matter, cause they are all lethal. There is only one genetic tetrasomy that permits the child to live, that of the X chromosome, which a strange case of Kleinefelter syndrome with the karyotype 44 + XXXY.
Likewise, there is only one viable double trisomy, that occurs for the X and Y chromosomes, known as the double male syndrome, which has the karyotype 44 + XXYY.
As you can see, things are a bit complex. However what you need to remember is the rule with chromosomes is not "the more the better", but "the exact number is best"

[Makubex]

Okay thanks for the replies guys, I think I get the idea now. So, we suppos that we still live as a species in a few millennias more, and we have evolved somehow. Would it then be possible that our species has more then 46 chromosomes as the standard number?

[victor]

based from what I've read in 'GENOME' book by Matt Ridley, the ancestor of ape men have 47 chromosomes. As the evolution runs along with it, the 3rd and the 4th chromosomes gets unified or simply said "combined" together to form the new 3rd chromosome.
Based on these sentences, they again emphasize that the exact number of chromosome is the best, not the more numbers.

@Andrew
XYY = Jacob's syndrome?

[MrMistery]

Jacob's? Could be. Never heard of it though... All my books just say "XYY syndrome"

[dipjyoti]

Down syndrome is a chromosome abnormality, usually due to an extra copy of the 21st chromosome. This syndrome usually, although not always, results in mental retardation and other conditions which alternative name is Trisomy 21.

[Ali Asim]

If a person has extra chromosome he is abnomal. i have read that if a person has one or more extra Y chromosome (Y chromosome is assosiated with maleness because of presence of SRY genes) then that person has criminal thinking instead of normal of brighten maleness character

[MrMistery]

i have also read that. However more recent book suggest otherwise. My genetics professor says that older books say that if you have more Y chromosomes result in criminal behaviour are the result of research conducted at alcatraz and sing-sing. No wonder they got to that conclusion...