ploidity

[JackBean]

In animals, apparently, if you have more chromosomes, you're in trouble (all the trisomies). On the other hand, many agricultural crops are polyploidy, so "if one gene is good, more genes are better". Why is that so? Or if the plant had only one chromosome in triplicate, would that be negative too?

[plasmodesmata11]

I'd say it's important because in plants it can give rise to new, perhaps superior species. This is a prominent way of sympatric speciation for plants. They can either diverge completely, filling a new niche, or they can compete in the same one and eihter succeed or fail. As to your last question, the its whole set would be triplicate, but i was under the impression it could only double (resulting in pairs at all times). I personally don't know much on that frontier though...

[JackBean]

I meant, that e.g. Down's syndrome is triplicate of only one chromosome (the others are diploid), so if that happend in the plant, would that be harmfull too? Probably yes.
Also, you raised good question. I was talking about triploidy (at least it sound so), but the crops are usually doubled, so would be triploidy harmfull even in plants?

[plasmodesmata11]

wow!
apparently there are crops that are triploid
look: http://en.wikipedia.org/wiki/Triploidy#cite_note-1
in the middle of the page... banana, apple, etc...
the watermelons are seedless...

[JackBean]

yeah, you're right, the seedless fruits are triploid...

So, do you think, that triploid/tetraploid animal could live?