Aneuploidy and polyploidy?

[Faraz]

Im still confused about the two, and is it true that nearly all polyploid babies dies before they are born?

[BA22]

yes, polyploid humans are not compatible with life, usually it results in a spontaneous abortion

[BA22]

polyploidy is an extra set of chromosomes, aneuploidy is a set less

[Faraz]

okay thats the thing in my book polyploidy is an extra set of chromosomes but for aneuploidy is said more or less, which doesnt make any sense unless its talking about 1 more or less sister chromatid not a complete set?

[Stephanie]

yea im confused about this still too, does anyone have a definition of each one??? that might help clarify

[bturville]

Polyploidy is when you have say...a diploid number of 4n instead of the usual 2n, polyploidy plants can often be more vigourous, but humans die before birth. So its a MULTIPLE of the normal number.

Aneuploidy is any number of chromosomes different to the norm, eg. Down syndromes, there are 3x 21 chromosomes, so you could call it chromosome 21 aneuploidy (trisomy, specifically). Extra or missing chromosomes, basically.

[Stephanie]

alrighty thanks... pretty simple actually i cant believe the text book didn't explain it

[Faraz]

okay okay I think I got it thanks

one more questions

in meiosis

does it go as the following?

4N ---> 2x 2N ----> 4x N?

and is mitosis

4N -----> 2x 2N ?

[bucket]

yes.

[bturville]

Yes, but remember the diploid number is 2n, and the haploid number (after meiosis) is n. 4n is sort of the number after DNA replication.

[Faraz]

yep I just wanted to make sure that in meiosis the chromosomes do double before the first split.